AI Search Glossary — Every Term Defined

AI search optimisation has its own vocabulary. This glossary defines every key term — from AEO and GEO to Speakable schema and crawl-to-referral ratios — with cross-references to our detailed guides. Bookmark this page as your reference for AI search terminology.

A

AEO (Answer Engine Optimisation)

AEO is the practice of optimising content to appear as direct answers in search engine features like featured snippets, voice assistant responses, and People Also Ask boxes. It predates the generative AI era and is narrower in scope than GEO. AEO focuses specifically on being the selected answer, not on appearing in synthesised multi-source responses.

See: AEO vs GEO vs LLMO comparison

AI Mode

AI Mode is Google's dedicated conversational search interface within Google Search, powered by Gemini. It allows users to ask follow-up questions and have multi-turn conversations while receiving AI-generated answers with cited sources. AI Mode represents Google's response to ChatGPT and Perplexity.

AI Overviews

AI Overviews are AI-generated summary answers that appear at the top of Google search results, triggered by approximately 48% of all queries. They exclusively cite pages that rank in Google's top 10 results. Multi-modal content (images, video) increases citation likelihood by 156%. Previously known as Search Generative Experience (SGE).

See: How to get cited in AI Overviews

Answer Capsule

An answer capsule is a 40-60 word factual paragraph placed immediately after a heading, designed to be extracted by AI platforms as a citation-ready response. Answer capsules contain specific data points, direct answers, and verifiable claims. When combined with Speakable schema, they become the primary extraction target for AI voice and text responses.

See: How to structure your website for AI crawlers

areaServed

areaServed is a schema.org property used in Organisation schema to specify the geographic area a business serves. AI platforms use areaServed to match businesses with location-specific queries. It accepts Country, State, City, or GeoShape values and is particularly important for local and regional businesses seeking AI visibility.

B

BreadcrumbList

BreadcrumbList is a schema.org type that defines the navigational hierarchy of a page within a website. AI crawlers use BreadcrumbList to understand site structure and the topical relationship between pages. It helps establish which pages are parent topics and which are subtopics, improving content categorisation during AI indexing.

See: Schema markup for AI search

C

ChatGPT

ChatGPT is OpenAI's conversational AI platform, holding 78% of the AI search market and generating 87.4% of all AI referral traffic. It indexes exclusively from Bing, not Google. Brand web mentions (0.664 correlation) and YouTube presence (0.737) are the strongest citation factors. ChatGPT processes approximately 2.5 billion prompts daily.

See: How to get cited in ChatGPT

Citation (AI)

In AI search, a citation is when an AI platform references, quotes, or attributes information to a specific source in its generated answer. Citations may include direct links (Perplexity, ChatGPT) or brand mentions without links (Claude, some Gemini responses). Citation tracking is the AI equivalent of rank tracking in traditional SEO.

ClaudeBot

ClaudeBot is Anthropic's web crawler that collects content for Claude's training data. It has a crawl-to-referral ratio of 23,951:1 — the worst among major AI platforms — meaning it crawls extensively but sends almost no referral traffic. Blocking ClaudeBot in robots.txt prevents your content from being included in Claude's training data.

See: How to get cited in Claude

Copilot (Microsoft)

Microsoft Copilot is an AI assistant integrated into Bing, Windows, Microsoft 365, and Edge. It uses Bing's search index, making it closely aligned with ChatGPT in terms of content discovery. Optimising for Bing visibility simultaneously improves visibility in both ChatGPT and Copilot.

Crawl-to-Referral Ratio

The crawl-to-referral ratio measures how many pages an AI platform crawls for every one referral visit it sends back. Perplexity has the best ratio at under 200:1. ChatGPT is approximately 1,000:1. Claude has the worst at 23,951:1. A lower ratio means the platform is more likely to send traffic to sources it cites.

See: Platform comparison with ratio data

E

E-E-A-T (Experience, Expertise, Authoritativeness, Trustworthiness)

E-E-A-T is Google's content quality framework that evaluates Experience, Expertise, Authoritativeness, and Trustworthiness. AI platforms — particularly Gemini and AI Overviews — inherit these signals from Google's index. Demonstrating E-E-A-T through author credentials, original data, and authoritative backlinks improves AI citation likelihood.

Entity SEO

Entity SEO is the practice of building a consistent, verifiable digital identity for a brand, person, or concept across multiple platforms. AI platforms cross-reference entity data from Organisation schema, Google Business Profile, Wikidata, LinkedIn, and other sources. Entity consistency is a prerequisite for AI visibility, particularly in Gemini.

See: How Gemini uses entity relationships

F

FAQPage Schema

FAQPage is a schema.org type that marks up question-and-answer content. It delivers a 350% increase in AI citation likelihood — the highest measurable impact of any schema type. AI platforms can directly extract structured Q&A pairs from FAQPage schema without parsing page content, making it the most effective schema for AI search.

See: Schema markup for AI search

G

Gemini

Gemini is Google's AI platform, drawing directly from Google's search index. It holds 8.65% market share, having overtaken Perplexity. Gemini actively uses schema markup to verify factual claims and weighs entity relationships via Google's Knowledge Graph heavily. Strong traditional SEO is a prerequisite for Gemini visibility.

See: How to get cited in Gemini

GEO (Generative Engine Optimisation)

GEO is the broadest and most commonly used term for AI search optimisation. It covers getting your content cited in AI-generated answers across all platforms — ChatGPT, Gemini, Perplexity, AI Overviews, Copilot, and Claude. GEO encompasses both traditional AEO tactics and newer AI-specific strategies like entity SEO and multi-index optimisation.

See: AEO vs GEO vs LLMO comparison | Best GEO agencies

GPTBot

GPTBot is OpenAI's web crawler used for collecting training data for GPT models. It is separate from OAI-SearchBot (which handles real-time ChatGPT search queries). Allowing GPTBot in robots.txt permits your content to be included in future model training. Blocking GPTBot does not prevent ChatGPT from citing you via Bing — OAI-SearchBot handles that.

I

IndexNow

IndexNow is a protocol that notifies search engines instantly when content is published or updated. Supported by Bing, Yandex, Seznam, and Naver (not Google). Since ChatGPT uses Bing's index, IndexNow provides near-instant content availability in ChatGPT search results, rather than waiting for Bing's normal crawl cycle.

See: Website structure for AI crawlers

Information Gain

Information gain is a concept where content provides unique data, insights, or perspectives not available elsewhere on the web. AI platforms favour content with high information gain because it adds to their knowledge base rather than duplicating existing information. Original research, proprietary data, and unique expert analysis all contribute to information gain.

K

Knowledge Graph

Google's Knowledge Graph is a database of entities (people, places, organisations, concepts) and the relationships between them. Gemini and AI Overviews use the Knowledge Graph to verify entity claims and understand relationships. Having your brand in the Knowledge Graph — via Wikidata, Wikipedia, or Google Business Profile — significantly improves AI visibility in Google's ecosystem.

L

LLMO (Large Language Model Optimisation)

LLMO is the most technical approach to AI search optimisation, focused specifically on how large language models absorb and retrieve information. It covers training data inclusion, RAG (retrieval-augmented generation), embedding optimisation, and model-specific behaviour differences. LLMO is most relevant for enterprise brands and technical products.

See: AEO vs GEO vs LLMO comparison

llms.txt

llms.txt is an emerging standard file placed at a website's root (like robots.txt) that provides AI models with a machine-readable index of the site's most important content. It tells AI crawlers what to prioritise during indexing. Adoption is early but growing, and major AI platforms are beginning to recognise it.

See: Website structure for AI crawlers

O

OAI-SearchBot

OAI-SearchBot is OpenAI's crawler specifically for real-time ChatGPT search queries, separate from GPTBot (which handles training data collection). When a ChatGPT user asks a question requiring current information, OAI-SearchBot fetches results from Bing. Blocking OAI-SearchBot prevents your content from appearing in ChatGPT's real-time search answers.

Organisation Schema

Organisation schema is a schema.org type that defines a business entity with properties including @id, name, sameAs, areaServed, and foundingDate. The @id property creates a persistent identifier that other schema blocks can reference. The sameAs property links to authoritative profiles (LinkedIn, Wikidata, GBP) that AI platforms use for entity verification.

See: Schema markup for AI search

P

Perplexity

Perplexity is an AI search platform holding 7% market share with the best crawl-to-referral ratio of any AI platform at under 200:1. It pulls 46.7% of its citations from Reddit, operates in real-time, and actively ignores promotional content. Perplexity abandoned advertising entirely and offers a Publishers' Programme with revenue sharing and citation analytics.

See: How to get cited in Perplexity | Perplexity Publishers' Programme

Person Schema

Person schema is a schema.org type that defines an individual with properties including name, jobTitle, worksFor, sameAs, and url. Pages with Article schema linked to a Person schema see a 3x increase in AI citation likelihood. Person schema connects content to a credentialed author, which AI platforms use as an expertise and trust signal.

See: Schema markup for AI search

Q

Query Fan-Out

Query fan-out is the process where AI platforms break a complex user query into multiple sub-queries, each answered independently before synthesising a combined response. AI Overviews and Gemini use query fan-out extensively. This means your content can be cited for a sub-query even if it doesn't directly match the original complex question.

R

RAG (Retrieval-Augmented Generation)

RAG is the technical process where an AI model retrieves relevant documents from an index before generating a response. ChatGPT uses RAG with Bing's index. Perplexity uses RAG with multiple sources. RAG is what allows AI platforms to cite current information rather than relying solely on training data. Optimising for RAG means optimising for the retrieval step — indexation, relevance, and content structure.

S

Speakable Schema

Speakable schema (SpeakableSpecification) marks content as suitable for text-to-speech and AI voice assistants. Despite delivering a 127% increase in AI citations, fewer than 10% of websites implement it. Speakable uses CSS selectors to target specific content blocks (like answer capsules) that AI platforms should prioritise for spoken responses.

See: Schema markup for AI search

SXO (Search Experience Optimisation)

SXO combines traditional SEO with user experience (UX) optimisation, focusing on the complete search journey from query to conversion. In the AI search context, SXO extends to ensuring that users who discover your brand through AI answers have a seamless experience when they visit your site. Page speed, mobile experience, and clear conversion paths all fall under SXO.

T

Topical Authority

Topical authority is the depth and breadth of content a website has on a specific subject. AI platforms favour sources that demonstrate comprehensive topic coverage over sites with isolated articles. Building topical authority means creating clusters of interlinked content that cover a subject from multiple angles, with internal links connecting related pages.

W

Wikidata

Wikidata is a free, structured knowledge base maintained by the Wikimedia Foundation. It provides machine-readable entity data that AI platforms — particularly Gemini — cross-reference for entity verification. Creating a Wikidata entry for your organisation with consistent data (name, description, location, sameAs links) strengthens your entity signal across all AI platforms.

What to do next

• Get a free AI visibility audit
• What is AI search optimisation?
• AEO vs GEO vs LLMO — which approach matters?
• Schema markup for AI search
• Compare all AI platforms
• How to structure your website for AI crawlers