SEO and AI search glossary

Plain-English definitions of SEO, GEO and AEO terms, from canonical tags and Core Web Vitals to query fan-out, llms.txt and AI citations.

3

301 vs 302 redirect: A 301 redirect tells browsers and search engines a page has moved permanently and the new URL should be treated as canonical, while a 302 signals a temporary move that keeps the original URL in search results.

A

AI agents: AI agents are AI systems that carry out multi-step tasks on a user's behalf, such as browsing websites, comparing options, filling in forms or making bookings, rather than only answering a question.
AI citation: An AI citation is a link or named source that an AI assistant or AI search feature shows alongside a generated answer to indicate where the information came from.
AI Mode: AI Mode is Google Search's conversational, AI-first results mode, where Gemini answers a query in depth, accepts follow-up questions and links to supporting web pages instead of showing a classic list of results.
AI Overviews: AI Overviews are AI-generated summaries that Google shows at the top of some search results, built from its search index and linking to the web pages that support the answer.
AI SEO: AI SEO is an umbrella term with two meanings: optimizing a site so it appears in AI-generated search answers, and using AI tools to do SEO work such as research, auditing and drafting.
AI share of voice: AI share of voice is the percentage of AI-generated answers, for a defined set of prompts, that mention or cite your brand, compared with competitors measured over the same prompts.
AI visibility: AI visibility describes how often and how accurately AI assistants and AI search features such as ChatGPT, Perplexity, Claude and Google's AI Overviews mention, recommend or cite a brand or website.
Answer Engine Optimization (AEO): Answer engine optimization (AEO) is the practice of structuring content so search features and AI assistants can lift a direct answer from it, from featured snippets and voice answers to AI-generated responses.

B

Backlink: A backlink is a link from a page on another website to a page on yours; search engines use links to discover pages and as one of many signals of how relevant and trusted a page is.
Brand mention: A brand mention is any reference to your brand, product or people on another website, forum, review site or video, whether or not it includes a link back to your site.

C

Canonical tag: A canonical tag is a link element with rel=canonical that tells search engines which URL you consider the main version of a page when the same or very similar content is available at several URLs.
ChatGPT-User: ChatGPT-User is the user agent OpenAI uses when ChatGPT or a custom GPT visits a web page because a person asked it to, rather than to crawl the web automatically.
ClaudeBot: ClaudeBot is Anthropic's web crawler for collecting public web content that may be used to train Claude models; Anthropic runs separate agents, Claude-SearchBot and Claude-User, for search and user requests.
Core Web Vitals: Core Web Vitals are three Google metrics for real-user experience: Largest Contentful Paint for loading, Interaction to Next Paint for responsiveness and Cumulative Layout Shift for visual stability.
Crawl budget: Crawl budget is the set of URLs a search engine can and wants to crawl on your site in a given period, determined by how much load your server can take and how much demand there is for your content.
Cumulative Layout Shift (CLS): Cumulative Layout Shift (CLS) is a Core Web Vitals metric that scores how much visible content unexpectedly moves while a page is open; a score of 0.1 or less is considered good.

D

Domain Authority (DA): Domain Authority is a third-party score from Moz, on a 1 to 100 scale, that predicts how likely a domain is to rank based mainly on its link profile; Google does not use it, and other tools publish similar scores.

E

E-E-A-T: E-E-A-T stands for Experience, Expertise, Authoritativeness and Trustworthiness, the framework Google's search quality raters use to assess content quality; Google says trust is the most important part.
Earned media: Earned media is coverage you do not pay for or publish yourself, such as press articles, reviews, forum recommendations and social shares, as opposed to owned media like your site and paid media like ads.
Entity: In search, an entity is a distinct, well-defined thing, such as a person, organization, place, product or concept, that a search engine can identify and connect to facts and to other entities, regardless of the exact words used.
Entity SEO: Entity SEO is the practice of helping search engines and AI systems recognize your brand, people and products as distinct entities, with consistent facts, clear relationships and corroborating sources across the web.

F

Featured snippet: A featured snippet is a highlighted excerpt from a web page that Google shows near the top of some results to answer the query directly, with a link to the source page.

G

Generative Engine Optimization (GEO): Generative engine optimization (GEO) is the practice of making your content easy for AI systems such as ChatGPT, Perplexity and Google's AI Overviews to retrieve, understand and cite when they generate answers.
Google-Extended: Google-Extended is a robots.txt product token, not a separate crawler, that lets publishers control whether content Google crawls may be used to train Gemini models and to ground answers in Gemini Apps and Vertex AI.
GPTBot: GPTBot is OpenAI's web crawler for collecting content that may be used to train its generative AI models; blocking it opts your site out of training but does not remove it from ChatGPT search.
Grounding: Grounding is the process of connecting an AI model's answer to verifiable source material, such as search results or a document set, so the response reflects current facts instead of only the model's training data.

H

hreflang: hreflang is an attribute that tells search engines which language and regional versions of a page exist, so each user can be shown the version that matches their language or country.

I

Indexability: Indexability is whether a search engine is allowed and able to add a page to its index, which depends on crawl access, status codes, robots rules, canonical signals and whether the content can be rendered.
Interaction to Next Paint (INP): Interaction to Next Paint (INP) is a Core Web Vitals metric that measures how quickly a page visibly responds to clicks, taps and key presses throughout a visit; 200 milliseconds or less is considered good.

J

JavaScript rendering: JavaScript rendering is the step where a crawler runs a page's JavaScript to build its final content; Google does this in a separate rendering stage, but most AI crawlers read only the initial HTML.
JSON-LD: JSON-LD (JavaScript Object Notation for Linked Data) is a format for adding structured data to a page inside a script tag, separate from the visible HTML; it is the format Google recommends for schema.org markup.

K

Keyword cannibalization: Keyword cannibalization happens when several pages on the same site target the same search intent, so they compete with each other and none ranks as well as a single consolidated page could.
Knowledge Graph: The Knowledge Graph is Google's database of entities and the relationships between them, used to power knowledge panels and to help Search understand what queries and pages are about.

L

Largest Contentful Paint (LCP): Largest Contentful Paint (LCP) is a Core Web Vitals metric that measures how long it takes for the largest image or text block in the viewport to render; 2.5 seconds or less is considered good.
LLM Optimization (LLMO): LLM optimization (LLMO) is the work of improving how large language models describe, recommend and cite your brand, both in answers drawn from live web search and in what models learned during training.
llms-full.txt: llms-full.txt is a companion file to llms.txt that contains the full text of a site's key pages, usually documentation, concatenated into one Markdown file so an AI tool can load everything in a single request.
llms.txt: llms.txt is a proposed Markdown file served at the root of a website that gives language models a short summary of the site and a curated list of links to its most useful content.

M

Meta description: A meta description is an HTML meta tag that summarizes a page; search engines may show it as the snippet under the title in results, but Google often generates its own snippet from the page content instead.

N

nofollow: nofollow is a rel attribute value that marks a link as one the site does not vouch for; since 2020 Google treats nofollow, sponsored and ugc as hints rather than strict instructions for ranking and crawling.
noindex: noindex is a robots rule, set in a meta tag or an X-Robots-Tag HTTP header, that tells search engines not to show a page in search results even though they are allowed to crawl it.
nosnippet: nosnippet is a robots meta rule that tells Google not to show a text snippet or video preview for a page, and that also stops the page's content being used as a direct input for AI Overviews and AI Mode.

O

OAI-SearchBot: OAI-SearchBot is the OpenAI crawler that finds and indexes web pages for ChatGPT's search features; sites that block it are not shown in ChatGPT search answers.
Orphan page: An orphan page is a page on your site that no other page links to internally, so users and crawlers can only reach it through a sitemap, an external link or by typing its URL.

P

Passage ranking: Passage ranking is a Google system that identifies individual sections of a web page to judge how relevant the page is to a search, so a strong answer buried in a long page can still be found.
People Also Ask (PAA): People Also Ask is a Google results feature listing related questions that expand to show a short answer from a web page, with more questions loading as users open them.
PerplexityBot: PerplexityBot is Perplexity's crawler for discovering and linking websites in Perplexity search results; Perplexity says it is not used to collect content for training AI foundation models.
Prompt volume: Prompt volume is an estimate of how often people ask AI assistants about a topic or phrase, offered by some AI visibility tools as the AI-search counterpart to keyword search volume.

Q

Query fan-out: Query fan-out is a technique AI search systems use to split one question into many related sub-queries, run those searches in parallel and combine the results into a single generated answer.

R

Redirect chain: A redirect chain is a sequence of two or more redirects between the requested URL and the final page, such as HTTP to HTTPS to www to a new path, which adds latency and wastes crawl requests.
Referring domain: A referring domain is a unique website that links to yours at least once; ten links from one site count as ten backlinks but only one referring domain.
Retrieval-Augmented Generation (RAG): Retrieval-augmented generation (RAG) is a method where a language model first retrieves relevant documents from an index or the web, then writes its answer using those documents, usually citing them.
Rich results: Rich results are Google search results enhanced with extra visual elements, such as review stars, prices, images or event dates, usually made eligible by structured data on the page.
robots.txt: robots.txt is a plain-text file at the root of a host that tells crawlers which URL paths they may or may not request, using rules grouped by user agent; it controls crawling, not indexing.

S

Scaled content abuse: Scaled content abuse is Google's spam policy term for generating many pages primarily to manipulate search rankings rather than to help users, whether the pages are produced by AI, by people or by other automation.
Spam Score: Spam Score is a third-party Moz metric estimating the percentage of sites with similar features to a given site that Moz found to be penalized or banned by Google; it is a correlation-based warning, not a Google signal.
Structured data: Structured data is machine-readable code, usually schema.org vocabulary written in JSON-LD, that describes what a page is about, such as a product, article, organization or event, so search engines can interpret it reliably.

T

Title tag: A title tag is the HTML title element in a page's head that names the page; search engines use it as the main source for the clickable headline in results, and browsers show it in the tab.
Toxic backlinks: Toxic backlinks is a term used by SEO tools for inbound links they judge spammy or manipulative; Google says it can usually ignore such links itself, and that disavowing is only for specific manual-action risks.

X

XML sitemap: An XML sitemap is a file that lists the URLs on a site you want search engines to discover, optionally with the date each page last changed, to help crawlers find new and updated content.

Z

Zero-click search: A zero-click search is a search that ends without the user clicking through to any website, because the answer was shown on the results page or the user refined or abandoned the query.