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Glossary

What is a Large Language Model (LLM)?

Updated September 2026Core ConceptBeginner

Definition

A large language model is a system trained on huge amounts of text to predict the next piece of text, one fragment at a time. The distinction from a reasoning model is effort: a reasoning model spends extra computation working through a problem before answering. Everything an assistant writes about your brand comes out of this prediction step.

At a glance

  • CategoriesCore Concept
  • Related fieldsAI Search
  • DifficultyBeginner

At a glance

  • An LLM predicts text. Every answer, summary and recommendation is that one operation repeated.
  • GPT, Claude, Gemini and Llama are all large language models, with different training data and different habits.
  • A model alone has no access to the live web. Search is a separate step bolted on around it.
  • The same prompt gives different wording twice, because the prediction is sampled rather than looked up.

Prediction, one fragment at a time

The model reads everything so far, the question plus whatever it has already written, and produces a distribution over what could come next. One fragment is picked. The whole thing runs again with that fragment added.

There is no plan and no draft. A model does not settle on a conclusion and write towards it. Coherence across a long answer comes out of each step being conditioned on every step before it.

The capability came from scale and from an architecture that weighs every part of the input against every other part, set out in Attention Is All You Need. Text is split into tokens and mapped into numbers, the representation behind an embedding. Nothing here is a lookup, and no stored copy of your site is being consulted.

Fluent by default, accurate only sometimes

Fluency and accuracy come from different places, and only one of them is guaranteed.

A model produces a clean, confident paragraph about your pricing whether or not it has seen your pricing page. Grammar is learned reliably. Facts about a mid-sized company are learned patchily, from whatever the training data happened to hold, and the model cannot tell the two apart.

This is why retrieval matters so much for brands. When an answer engine fetches your live page and puts it in front of the model, the model is summarizing a real document. With nothing fetched, it reconstructs you from a blurry memory, and the output looks identical either way. Your content is not competing to be memorised. It is competing to be the document handed over at the moment somebody asks.

Give a model less room to improvise

You cannot change the model. You can change how much guessing it has to do.

  1. Put the fact in one plain sentence. “Plans start at 49 dollars a month.” A model summarizing that has nothing to invent. A pricing table rendered as an image gives it everything.
  2. Keep claims next to their qualifiers. If a price depends on annual billing, say so in the same sentence. Split across two sections, the qualifier gets dropped in the summary.
  3. Cut the marketing phrasing. Superlatives and vague benefit copy compress badly. A model paraphrasing “the fastest platform on the market” returns something you would not have signed off.
  4. Repeat the core facts on every page that gets fetched. Product, pricing, about. Each stands alone, because each gets retrieved alone.
  5. Read your page as a stranger would. If a person skimming for thirty seconds could get your category wrong, so can a model.

Frequently asked questions

  • Is a large language model the same thing as AI search?

    No. The model writes the answer. AI search is the whole system around it: deciding whether to search, running the searches, picking passages, handing them to the model, and rendering citations. ChatGPT with search off and ChatGPT with search on use the same model and behave very differently.

  • Does an LLM actually know facts about my company?

    Some, unevenly, and it cannot tell you which. Facts repeated widely across the web tend to be learned. Facts stated once on your own site usually are not. Any answer mixes learned material with whatever was retrieved in that conversation, and nothing marks which is which.

  • Can I stop an LLM training on my content?

    Partly. Robots directives let you block the named training crawlers that honour them, and the major labs document theirs. That removes nothing already inside a trained model, and it does not cover content republished elsewhere. Blocking usually costs you retrieval too, which is the part driving citations.

  • Do I need to understand how an LLM works to market a brand?

    At this level, yes. Past it, no. Knowing that answers are predicted rather than looked up changes how you write a page. Knowing parameter counts changes nothing you will ever do. Learn the shape, skip the internals, spend the time on your pages.