SEO glossary: 120 SEO terms explained simply

An SEO glossary gathers the vocabulary of search engine optimisation, with a short definition for each term. This one gives 120 terms, sorted alphabetically within four families: technical, content, link building, and GEO and AI. Each entry fits in one or two sentences and points to a detailed guide on the site when there is one. Use the search box below to find a term in a few seconds.

How to use this SEO glossary

SEO terms: four families, one alphabetical order

Each family has its own section, and the terms within it follow the order of the alphabet. A word appears only once, in the family where it is most useful. Acronyms (LCP, INP, SERP, RAG) are given exactly as you will see them in your tools and in Google’s documentation.

SEO vocabulary: how to read a definition

Each definition answers a single question: what it is for, and what to watch out for. When a topic needs more room, a link sends you to the full guide on the site. The thresholds quoted (2.5 seconds, 200 ms, 0.1) are the ones Google publishes for Core Web Vitals on web.dev.

Technical SEO glossary: crawling, indexing and performance

Technical SEO covers everything that lets Google find, read and store your pages: crawling, indexing, speed, redirects and tags. These terms are the most useful when an audit flags an error in Search Console.

Technical terms from numbers to C

301 redirect: a permanent redirect from one URL to another. It passes most of the ranking value to the new address.

302 redirect: a temporary redirect. It signals that the old URL will come back, so it is not meant for moving a page for good.

404 status code: the server response saying a page does not exist. A few 404s are normal; a mass of internal 404s is not.

Breadcrumb: the navigation path shown at the top of a page (Home > Blog > Article). It helps users and strengthens internal linking.

Canonical tag: a tag that tells Google which URL represents a page when several addresses show identical or very similar content. Further reading: canonical tag guide.

CDN: a network of servers spread around the world that delivers your files from the point closest to the visitor, so faster.

Cloaking: showing different content to robots and to visitors. Google lists it among spam practices.

CLS: Cumulative Layout Shift: measures unexpected layout shifts while the page loads. Target: 0.1 or less.

Core Web Vitals: three page experience metrics chosen by Google: LCP, INP and CLS. They are assessed on real visitor data.

Crawl budget: the number of pages Googlebot is willing to crawl on your site over a given period. It mostly matters for very large sites.

Crawling: the exploration of a site’s pages by a robot that follows links to discover them. It is the step before indexing.

Technical terms from G to N

Googlebot: Google’s crawler. It comes in a mobile and a desktop version, the mobile one being the main one.

Heading tags: the H1 to H6 headings of a page. They organise the content for readers and robots alike.

hreflang: an attribute that connects the versions of the same page in several languages or countries, so each visitor gets the right one.

HTTPS: the secure version of the HTTP protocol, enabled by a certificate. Google treats it as a light signal, and browsers warn users without it.

Indexing: the storing of a page in Google’s database. A crawled page is not necessarily indexed.

INP: Interaction to Next Paint: measures how quickly the page responds to clicks and typing. Target: 200 ms or less.

JavaScript SEO: the set of good practices that ensure JavaScript-generated content is properly rendered, crawled and indexed.

LCP: Largest Contentful Paint: the time it takes to display the largest visible element of the page. Target: 2.5 seconds or less.

Meta robots: a tag that gives a page indexing and display instructions: noindex, nofollow, nosnippet.

Mobile-first indexing: Google indexes and ranks pages based on their mobile version. Content missing on mobile counts for nothing.

Noindex: an instruction asking Google not to index a page. It only works if the page remains crawlable.

Technical terms from R to X

robots.txt: a file at the root of the site that tells robots which areas not to crawl. It blocks crawling, not indexing. Further reading: robots.txt tester.

Schema.org: the shared vocabulary search engines use to describe content: Article, Product, FAQPage, Organization.

Search Console: Google’s free tool that shows the queries, clicks, indexing errors and issues of your site.

Server log: a file that records every visit, robots included. Analysing it shows what Googlebot really crawls.

Site migration: a change of domain, URLs or structure, backed by redirects, to keep the rankings already earned.

Slug: the end of a URL that names the page (for example /seo-glossary/). Short and descriptive, it is chosen once and for all.

Soft 404: a page that returns “200 OK” while showing nothing useful (empty page, discontinued product). Google ends up treating it as a 404.

Structured data: code added to a page to describe its content to Google (product, review, recipe, article). It can make the page eligible for rich results.

Title tag: the page title in the HTML head. It often becomes the clickable link in search results.

TTFB: Time To First Byte: the delay before the server sends the first byte. A high TTFB slows down everything else that loads.

XML sitemap: a file that lists a site’s important URLs to help Google discover them. It is never mandatory.

Content and keyword glossary

This family covers what you write and how people search for it: keywords, intent, page structure and quality signals. Content SEO vocabulary helps you choose a topic, cover it and keep it up to date.

Content terms from A to K

Algorithm: a set of automatic rules that decides the order of results. Google combines several of them, updated constantly.

Bounce rate: the share of visits that end after a single page. On its own, this figure does not tell you whether the visitor found an answer.

Content gap: the difference between the topics your competitors cover and the ones you cover. It is a source of new articles.

Content refresh: updating an old article (figures, examples, structure) to regain or strengthen its ranking.

Core update: a major update to Google’s algorithm, several times a year. It reassesses the perceived quality of sites.

CTR: click-through rate: clicks divided by impressions. A good title and a good meta description push it up.

Duplicate content: identical or very similar text found on several URLs. It dilutes rankings and is handled with a canonical tag or a redirect. Further reading: canonical tag.

E-E-A-T: experience, expertise, authoritativeness and trustworthiness: the criteria Google’s quality raters apply to content.

Featured snippet: an extract highlighted at the top of the results that answers the question directly.

Internal linking: links from one page of your site to another. They spread authority and guide robots.

Keyword: a word or phrase the searcher types. It is also called a query when talking about search.

Keyword cannibalisation: two pages of the same site targeting the same query and competing instead of reinforcing each other.

Keyword density: the share of a keyword in a text. It is no longer a numerical target: you write for the reader.

Keyword difficulty: a score, specific to each tool, that estimates the effort needed to rank for a query. It varies from one tool to another.

Keyword stuffing: artificial repetition of keywords to manipulate rankings. Google identifies it as spam.

Content terms from L to Z

Long tail: specific, long and infrequent queries. Taken together, they often weigh more than the big keywords.

Meta description: a short summary shown under the title in the results. It has no direct effect on rankings but influences clicks.

On-page optimisation: everything you adjust on the page itself: title, headings, text, images, internal links, tags.

People Also Ask: a block of related questions that expand in the results. You work on it with headings phrased as questions.

Pillar page: a reference page that covers a topic broadly and links to more detailed pages.

Query: the words typed into the search bar. A single page can rank for dozens of queries.

Rich snippet: an enhanced result: review stars, price, cooking time. It is obtained with structured data.

Search intent: what the searcher really wants: to learn, to compare, to buy or to reach a specific site.

Search volume: the average number of times a query is typed per month. It is an estimate provided by the tools.

Semantic cocoon: a way of organising pages into themes connected by internal links, to show Google that a topic is covered coherently.

Semantic field: all the words and phrases that revolve around a topic. A thorough text covers them naturally.

SERP: Search Engine Results Page: a search engine’s results page, with its blocks and ads.

Thin content: a page that gives the reader too little: a few lines, generic text, no useful information.

YMYL: Your Money or Your Life: health, money or legal topics, where a mistake can harm the reader. Google demands more reliability there.

Zero-click search: a search that ends on the results page, because the answer is already displayed there.

Link building, authority and risky practices glossary

Links remain a central ranking signal. This part of the glossary brings together the vocabulary of link building, the authority metrics of SEO tools and risky practices, from the cleanest to the most abusive.

Link building terms from A to L

Anchor over-optimisation: too many links with exactly the same keyword as anchor. A natural profile varies its wording.

Anchor text: the clickable text of a link. It tells Google and the reader what the destination page contains.

Backlink: a link from another site to yours. It is the historical popularity signal of SEO.

Black hat: techniques that get around Google’s rules to climb quickly, at the risk of a penalty.

Brand mention: a mention of a brand name without a link. AI engines and Google can associate it with the entity concerned.

Citation Flow: a Majestic metric that estimates the volume of a site’s popularity from the number of links it receives.

Co-citation: two sites mentioned together on the same third-party page, without a link between them. It brings their topics closer.

Contextual link: a link placed in the body of a text, surrounded by relevant words. It is the most natural and most sought-after form.

Disavow: a file sent to Google asking it to ignore toxic links. Keep it for cases of a confirmed penalty.

Dofollow link: an ordinary link, with no particular instruction. It can pass popularity to the target page.

Domain authority: a score specific to each tool (DA, DR, AS) that estimates the strength of a site. Google does not use it as such.

Grey hat: the grey area between good practice and abuse, such as discreetly buying links on quality sites.

Guest post: an article published as a guest on another site, with a link to yours.

Link building: all the actions aimed at earning inbound links: shareable content, press relations, partnerships.

Link exchange: an agreement where two sites link to each other. Done at scale, it becomes link spam.

Link building terms from L to W

Link juice: an image for the popularity passed by a link from one page to another.

Link profile: all the inbound links of a site: where they come from, their anchors and the pace at which they appear.

Linkbaiting: creating content remarkable enough for other sites to cite it spontaneously: a study, a tool, an infographic.

Manual action: a penalty applied by a person at Google, reported in Search Console with the reason given.

Netlinking: the word used in France and much of Europe for acquiring external links to a site, through exchanges, purchases or citable content.

Nofollow link: a link marked rel nofollow, asking Google not to follow it as an endorsement. Google treats it as a hint.

Outbound link: a link from one of your pages to another site. Citing good sources is part of quality content.

PBN: Private Blog Network: a network of sites built to manufacture links. Google fights it as link spam.

Penguin: a Google algorithm launched in 2012 against artificial links, folded into the core system in 2016.

Referring domain: a single site that links to yours. Ten links from the same site count as one referring domain.

Sponsored link: a link published as part of a paid partnership, most often within a guest article on a site covering the same topic.

Trust Flow: a Majestic metric that estimates a site’s trustworthiness from how close its links are to trusted sites.

UGC link: a link left by users (comments, forums), to be marked rel ugc.

White hat: techniques that follow Google’s guidelines, built on the quality of the content and of the experience.

GEO and AI glossary: the vocabulary of answer engines

Answer engines and AI assistants have added their own language to SEO. These GEO definitions help you understand how a page is read, split into passages and then cited in a generated answer.

GEO and AI terms from A to G

AEO: Answer Engine Optimization: optimising to be the answer given directly by an answer engine or an assistant.

AI citation: a mention of your page as a source in an answer generated by an assistant (link, brand name or extract).

AI Mode: Google’s conversational search mode, which answers with a synthesis and accepts follow-up questions.

AI Overviews: AI-generated summaries at the top of some Google results pages, with links to the sources cited.

AI share of voice: how often a brand is cited in AI answers, compared with its competitors on the same set of questions.

AI visibility tracking: regular measurement of a brand’s presence in assistants’ answers, using a list of tested questions.

Answer engine: a tool that answers a question with a sourced synthesis rather than a list of links: Perplexity, ChatGPT Search.

Chunk: a short passage of text, cut out by an AI system so it can be retrieved and cited. A clear heading helps this splitting.

Content freshness: the date and timeliness of a piece of information. AI assistants often favour recent sources on topics that change.

Embedding: a numerical representation of the meaning of a text. AI engines use it to match a question with relevant passages.

Entity: a person, brand, place or concept that search engines identify unambiguously, whatever words are used to write it.

Extractable content: text written to be quoted as is: the answer at the top of the section, self-contained sentences, dated and sourced figures.

GEO: Generative Engine Optimization: optimising to be cited in the answers of generative AI engines.

Google-Extended: a robots.txt token that lets you refuse the use of your pages by some of Google’s generative AI products. Further reading: robots.txt tester.

GEO and AI terms from G to Z

GPTBot: OpenAI’s crawler. You allow or block it in the robots.txt file. Further reading: robots.txt tester.

Hallucination: information made up by a language model and presented as true. Citing reliable sources limits the risk.

Knowledge Graph: Google’s knowledge base that connects entities to one another. It feeds knowledge panels and some answers.

LLM: Large Language Model: a language model trained on huge volumes of text, such as those behind ChatGPT, Gemini or Claude.

llms.txt: a file proposed at the root of a site to guide language models towards its important pages, in plain text.

Passage ranking: Google’s ability to rank a specific passage of a page rather than the whole page.

Perplexity: an answer engine that cites its sources in numbered notes. It is one of the assistants to monitor in GEO.

Prompt: an instruction or question sent to an AI. Users’ prompts are often longer than classic queries.

Query fan-out: a technique where the AI splits a question into several parallel searches before composing its answer.

RAG: Retrieval-Augmented Generation: the AI fetches up-to-date documents before answering, which lets it cite web pages.

SGE: Search Generative Experience: the original name of Google’s generative answers, which became AI Overviews.

Token: the unit of text processed by a language model: a word, part of a word or a punctuation mark.

Topical authority: recognition of a site as a reference on a specific topic, thanks to complete and coherent coverage.

Zero-click visibility: a brand’s presence in an answer without a visit to the site. It is measured in awareness, not in traffic alone.

Which SEO terms get confused most often?

A few pairs of terms look alike and yet do different things. Here are the ones behind the most configuration mistakes.

• Crawling and indexing: a page can be crawled without being stored in Google’s index.
• robots.txt and noindex: the first prevents crawling, the second prevents indexing. Blocking a page in robots.txt stops Google from reading its noindex.
• Nofollow and noindex: one applies to a link, the other to a whole page.
• 301 and 302 redirects: the first is permanent, the second temporary.
• SEO and GEO: the first aims for a ranking in a list of results, the second for a citation in a generated answer.