GEO glossary: 30 terms for the AI-search era
Updated June 25, 2026 · 6 min read
This glossary defines the core terms of the AI-search era in plain language — Generative Engine Optimization (GEO), Answer Engine Optimization (AEO), retrieval-augmented generation (RAG), AI Overviews, llms.txt, AI share of voice, and the rest. Use it as a quick reference when planning or measuring your AI-search visibility.
Key takeaways
- GEO is the practice of earning citations inside AI-generated answers.
- RAG is the retrieval step that lets engines ground answers in your content.
- Citation and AI share of voice replace clicks and rankings as core GEO metrics.
- Most terms describe parts of one system: retrieve, synthesize, cite, measure.
Core concepts
Start with the terms that frame the whole field.
- Generative Engine Optimization (GEO): structuring content so AI answer engines cite your brand as a source.
- Answer Engine Optimization (AEO): structuring a passage to be extracted as the direct answer, on snippets, voice, or AI surfaces.
- Answer engine: any system that returns a synthesized answer instead of a list of links (ChatGPT Search, Perplexity, AI Overviews).
- Generative engine: an AI system that composes a new answer from retrieved sources rather than quoting one.
- Citation: a named, linked source the engine attributes part of its answer to — the GEO win condition.
How engines find and use content
These terms describe the retrieval and grounding machinery behind an AI answer.
- Retrieval-augmented generation (RAG): retrieving relevant content at query time and grounding the generated answer in it.
- Retrieval: the step where an engine searches an index and pulls candidate passages relevant to the query.
- Chunk: a passage-sized piece of your content that gets indexed and retrieved independently.
- Embedding: a numeric vector representing a chunk's meaning, used to match it to a query.
- Grounding: anchoring a generated answer to retrieved evidence to keep it accurate and citable.
- Hallucination: a confident but unsupported or false statement a model produces without grounding.
- Parametric knowledge: what a model learned during training, frozen at its cutoff date.
Surfaces and crawlers
Where AI answers appear, and the bots that fetch the content behind them.
- AI Overview: Google's AI-generated summary at the top of results, synthesized from its index and linked to sources.
- Featured snippet: a single source quoted verbatim at the top of results.
- Zero-click search: a search satisfied on the results surface, with no click to a site.
- llms.txt: a proposed plain-text file that points AI crawlers to your most important, answer-ready pages.
- robots.txt: the file that allows or blocks crawlers — including AI bots — from fetching your pages.
- GPTBot / OAI-SearchBot: OpenAI's crawlers; allow them to be eligible for ChatGPT Search citations.
- PerplexityBot: Perplexity's crawler; allow it to be eligible for Perplexity citations.
- Structured data (JSON-LD): machine-readable markup stating a page's entities and facts so engines parse it cleanly.
Strategy and measurement
The terms you'll use to plan content and prove impact.
- AI share of voice: how often you're cited versus competitors for your target questions.
- Answer-first content: writing that states the direct answer near the top, before context.
- Entity SEO: making your brand a clear, consistent entity engines can recognize and disambiguate.
- Topical authority: depth and breadth across a subject that signals you're a trusted source on it.
- E-E-A-T: experience, expertise, authoritativeness, and trustworthiness — quality signals engines lean on.
- Brand Memory: a consistent source of truth about your business that grounds accurate AI descriptions of it.
- Share of model: a brand's presence across AI answers for a category, the AI-era analog of share of search.
Frequently asked questions
What's the difference between GEO and AEO in one line?
AEO makes a passage extractable as the answer; GEO is the broader practice of earning citations across AI engines, which includes AEO plus authority and machine-readability.
Is llms.txt an official standard?
It's a community proposal, not a universally adopted standard. It's low-cost to add and can help AI crawlers find your best pages, but on its own it doesn't guarantee citations.
Which term should I track as my main GEO metric?
AI share of voice — how often you're cited versus competitors for your target questions — is the closest single measure of GEO success, complemented by AI-referral traffic and leads.
Put this into practice — free.
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