Large language model

Models Beginner Also called: LLM

Definition

The kind of AI model behind ChatGPT, Claude, and Gemini. It was trained on an enormous amount of text and got very good at predicting what words come next, which at scale turns into answers, summaries, translations, and code. It is fluent whether or not it is right, so it needs checking.

In plain English

An LLM read more text than any human could and got very good at guessing what comes next. Guess the next word well enough, long enough, and you get answers, summaries, and code.¹ That’s the whole thing. The rest is scale.

In the real world

Every chat assistant: ChatGPT, Claude, Gemini.
Autocomplete in your email that finishes the sentence.
The “summarize this thread” button.

When to use it

Anything made of language. Drafting, rewriting, summarizing, translating, explaining, turning notes into a plan.

When not to use it

Math and exact lookups. Use a calculator or a spreadsheet, or a model with tools that can.
As a source of truth. It produces plausible text, not verified text. See hallucination.

Good, bad, ugly

Good: it speaks your language. Literally. Nothing to learn before you start.
Bad: it’s fluent whether or not it’s right.
Ugly: fluency reads as competence, and people stop checking.

Key facts

Trained on: Huge amounts of text, then tuned to be helpful
Core trick: Predicting what text comes next, at a scale where that becomes useful
Examples: GPT, Claude, Gemini, Llama, DeepSeek

Common questions

Is an LLM the same as AI?

No. It's one kind of AI model, the kind that works with language. It happens to be the kind behind the chat tools everyone uses.

Does it understand what I say?

It predicts text extremely well from patterns in its training data. Whether that counts as understanding is a philosophy debate. In practice, treat it as a very well-read assistant that sometimes guesses.

Why does it make things up?

Because it produces likely text, not checked text. See hallucination.

References

Large language modelWikipediaView source
Glossary: LLMAnthropic, Claude Platform DocsView source