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Knowledge Base

The terms and mechanics behind AI search — explained plainly.

Short, honest definitions — not marketing copy. Where something is genuinely uncertain or platform behavior isn't publicly documented in detail, we say so rather than guess.

Core concepts

SEO — Search Engine Optimization

The practice of making a website easier for traditional search engines (Google, Bing) to crawl, index, and rank — technical health, on-page content quality, and off-site authority (backlinks, mentions). Every other term on this page builds on SEO fundamentals; none of them replace it.

AEO — Answer Engine Optimization

Structuring content so a system looking for a direct answer — a featured snippet, a voice assistant, an FAQ block — can extract one cleanly: a clear question, a direct answer near the top, then supporting detail. See our FAQ Schema Generator.

GEO — Generative Engine Optimization

Improving how generative AI systems (ChatGPT, Perplexity, Gemini, Claude, Google AI Overviews) understand, retrieve, and cite a business when answering a user's question — not through a special trick, but through genuine crawlability, clear entity signals, and content worth citing. Our Answer Index measures this directly, across real platforms, rather than estimating it.

XEO — Experience Engine Optimization

An emerging, less standardized term for making content surface well across the full range of "answer experiences" a user might encounter — search results, AI chat answers, voice assistants, and AI agents — rather than optimizing for one channel at a time. Because it's newer and less formally defined than SEO or GEO, treat any confident claim about "XEO best practices" with some skepticism, including this one.

LLMO — Large Language Model Optimization

Making sure content is genuinely legible and unambiguous to a language model reading it — clear entity names, explicit relationships ("X provides Y in Z"), and content that doesn't rely on visual layout or context a model reading raw text would miss.

Entity

A specific, identifiable thing — a company, a person, a place, a service — that a search or AI system can recognize and connect information to consistently. A business becomes a well-formed entity when its name, description, services, location, and contact details are stated the same way everywhere: on its own site, in its schema markup, and across external profiles.

Structured Data / Schema Markup

Machine-readable markup (usually JSON-LD, using the schema.org vocabulary) added to a page to state explicitly what's already visible on it — "this is an Organization named X," "this is a Service called Y." It doesn't replace real content, and Google is explicit that there's no special schema type required for AI Overviews or AI Mode — schema should describe what's genuinely there, not manufacture eligibility for a feature. Check any page's schema with our Schema Markup Validator.

Knowledge Graph

A structured map of entities and the relationships between them (this company → offers → this service → in → this location). Search engines and AI systems build and consult knowledge graphs to answer questions about specific entities rather than just matching keywords.

E-E-A-T — Experience, Expertise, Authoritativeness, Trustworthiness

Google's framework (from its Search Quality Rater Guidelines) for judging whether content demonstrates real, first-hand experience and genuine expertise, and whether the site and author are authoritative and trustworthy. It's a set of quality signals for human raters and ranking systems to weigh, not a checklist or a schema type to implement.

AI Crawler

An automated bot an AI company runs to fetch web pages — for training data, for live search retrieval, or both, depending on the crawler. GPTBot and OAI-SearchBot (OpenAI), ClaudeBot (Anthropic), and PerplexityBot (Perplexity) are the current major ones; each respects robots.txt, so a site has to explicitly allow the ones it wants reaching it. Check whether a site actually allows them with our AI Crawler Access Checker.

AI Citation

The moment an AI system names or links to a specific business in its answer to a user's question — the actual outcome GEO work is trying to earn. It's binary and observable (a business was cited in a given run, or it wasn't), which is why we measure it directly in the Answer Index rather than inferring it from traffic or rankings.

llms.txt

A proposed convention (not a formal web standard, and not required by Google, OpenAI, or Perplexity) for a plain-text file at a site's root summarizing what the site is and linking its most important pages, meant as a quick brief for an AI agent. Worth having — ours is here — but it's a minor, optional convenience layered on top of real crawlability and content, not a substitute for either. See our take in the Editorial Policy.

How the major AI platforms actually find and cite content

These platforms don't publish full technical detail on their retrieval and citation logic, and it changes over time. What follows is what's publicly documented or stated by each company — not reverse-engineered guesswork.

Google AI Overviews & AI Mode

Google states these features are built on the same foundational systems as Google Search — the same crawling (Googlebot), indexing, and ranking signals that determine regular search visibility, plus generative summarization on top. Google is explicit that there's no separate technical requirement or special schema needed specifically for AI Overviews or AI Mode beyond good, crawlable, helpful content. Google-Extended is a separate control specifically for whether Google can use a site's content to improve Gemini and Vertex AI generative models — distinct from whether Googlebot can crawl the site for Search at all.

Perplexity

Perplexity operates PerplexityBot for crawling and has stated it respects robots.txt directives. Perplexity's core product is answer synthesis with inline citations, so a page being both crawlable and clearly citable (a specific, extractable claim rather than only a vague pitch) matters directly to whether it gets used as a source.

Claude

Anthropic operates ClaudeBot for crawling and Claude-User/anthropic-ai for other access patterns depending on the product surface (for example, when Claude fetches a page live in response to a user's request). As with the others, robots.txt allow rules determine whether a given crawler can reach a site at all.

Microsoft Copilot / Bing

Copilot's web-grounded answers draw on Bing's index, built by Bingbot. The same fundamentals apply: a page has to be crawlable and indexed by Bing before it can ever be retrieved for a Copilot answer.

Want to check whether your own site actually allows these crawlers, and whether your structured data is valid? Run our free tools →