The AI Search Glossary: AEO, GEO, LLMO & More

AI search introduced a new vocabulary, and much of it overlaps or competes. This glossary defines the terms in plain English, notes where they mean the same thing, and links to fuller guides. Start with the answer engine optimization pillar if you want the concepts in context, or read how AI is changing SEO for the bigger picture. Otherwise, use the groups below as a reference.

These three terms describe the same emerging practice, earning visibility inside AI answers, from slightly different angles.

Answer engine optimization (AEO) is structuring and publishing content so AI answer engines cite your brand in the answers they generate. Where SEO competes for clicks on a results page, AEO competes to be the source an AI quotes.

Generative engine optimization (GEO) is optimizing content to be surfaced and cited by generative AI search tools. It's a near-synonym for AEO that leans on the generative nature of the engines.

LLMO, or LLM SEO, is large language model optimization: getting your content mentioned and cited by large language models and the AI tools built on them. It's used interchangeably with AEO and GEO. (Fun fact: the name Elmo comes from LLMO.)

AI search engine is a tool that answers a query with a synthesized, usually-cited response instead of a list of links, like Perplexity, ChatGPT Search, or Google's AI Overviews.

Answer engine is any system that responds to a question with a direct answer rather than a list of sources to evaluate. AI search engines are answer engines, and the term now usually refers to them.

AI Overviews are Google's AI-generated summaries shown above traditional search results for many queries, built on its Gemini models and linking to sources.

AI visibility is how present and accurately represented a brand is across AI answers: how often it's mentioned, how often it's cited, and how it's described. Measuring and improving it is the focus of AI visibility software.

Citation (in AI search) is a link or source reference an AI answer attributes information to. Citations are the unit of visibility in AI search: being cited can send traffic, and it signals that the engine trusts your content.

Prompt volume is the number of distinct prompts, or questions, you track across AI engines. AI visibility tools meter usage by prompt volume, and broader coverage gives a more reliable read on your presence.

Share of voice (AI) is the share of relevant AI answers that mention your brand versus competitors. A higher share means engines name you more often than rivals for the prompts that matter.

Entity is a distinct, identifiable thing (a brand, person, product, or concept) that search and AI systems recognize and connect to others. Clear, consistent entity information helps engines resolve and trust your brand.

Structured data (schema) is machine-readable markup, using schema.org vocabulary, that labels what content is: an article, an FAQ, an organization, a how-to. It helps engines parse and reuse your content accurately.

Retrieval-augmented generation (RAG) is a method where an AI system retrieves relevant sources, then generates an answer grounded in them. Most AI search engines use RAG, which is why being retrievable and quotable is central to AEO.

Grounding is tying an AI's answer to specific external sources so it reflects real, current information rather than the model's memory alone. Grounded answers are likelier to cite the sources they used.

Hallucination is when an AI generates confident but false or unsupported information. For brands, that can mean inaccurate claims about your product, which is one reason to monitor how AI describes you.

For practical purposes, yes. Answer engine optimization, generative engine optimization, and LLM optimization all describe the work of getting your brand surfaced and cited inside AI-generated answers. The differences are emphasis, not substance:

You'll see all three used as synonyms across the industry, and none of them should change what you actually do. If you're building a strategy, pick one term for consistency and focus on the shared playbook: answer questions directly, structure content for extraction, build entity authority, earn trusted citations, and measure the results. The AEO guide and generative SEO guide cover that playbook in full, and the best AI visibility tools roundup covers how to measure and optimize your performance in AI search.