AI SEO Glossary

A Large Language Model is a type of AI trained on massive amounts of text data to understand and generate human language. LLMs like GPT-4, Gemini, and Claude learn patterns across billions of documents and can answer questions, summarize content, write text, and reason through problems. In the context of search, LLMs are the engines powering AI Overviews, Perplexity answers, and ChatGPT Search responses. When one of these tools answers a question about your industry, your brand, or your product, the LLM is deciding what to say based on what it has learned and what it can retrieve.

The major LLMs powering AI search today include GPT-4o and GPT-4.5 behind ChatGPT Search, Google’s Gemini models behind AI Overviews and AI Mode, Anthropic’s Claude behind Claude.ai’s search features, Meta’s Llama models used in various third-party search tools, and Perplexity’s own combination of models including Sonar. Each model has different training data, retrieval logic, and citation behavior, which is why your brand may appear consistently in one platform and be absent in another. Monitoring across models is the only way to get a complete picture.

Why it matters: The LLM is the gatekeeper between your content and the user. Understanding how it works is the foundation of everything in AI SEO.