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Foundations

LLM

also called Large Language Model

A very large model whose only job, at heart, is predicting the next token.

Definition

A language model with billions of learned parameters, trained on enormous amounts of text so that predicting the next token forces it to internalise grammar, facts, style and a surprising amount of reasoning.

Everything an LLM does — answering, coding, summarising, calling tools — is generation, one token at a time, each time conditioned on everything before it. Keep that in mind and its behaviour stops being mysterious.

The single most useful thing to internalise is that the model is a next-token predictor, and that everything else — following instructions, using tools, refusing, apologising — was layered on top of that one objective by later training. When a model does something strange, the base objective is usually the explanation.

How people use it
Setting expectations before a demo.
"It is an LLM, so it will be confidently fluent even when it is wrong. That is a separate problem from accuracy."
Worked examples

Predicting plausible text is not the same as knowing

An assistant invents a plausible-sounding function name that does not exist.

The completion was locally plausible — that is exactly what the objective rewards. The fix is architectural, not a stern instruction: give it the file to read, or a tool to check, so plausibility has something to be measured against.

Scaling bought in-context learning

Why a prompt with three examples works at all.

Larger models began doing few-shot learning from examples in the prompt without any weight updates, which turned prompting into a discipline overnight. It is also why "just describe the format" became a substitute for training a model — up to a point.

Avoid

Treating the model as a database. It stores a lossy impression of its training data, not records.

Sources
  • paperLanguage models are few-shot learners ↗OpenAI (arXiv) · 2020

    Introduces GPT-3 at 175B parameters and shows that scale alone produced in-context learning: performance from examples in the prompt, with no gradient updates.

  • guideIntroduction to large language models ↗Google for Developers · 2026

    A plain-language official introduction to models, tokens and context. Teaching material rather than origin research — good for the definition, not for a claim about the frontier.

  • paperWhy language models hallucinate ↗arXiv (OpenAI researchers) · 2025

    The statistical argument that training and grading regimes reward guessing over admitting uncertainty — so hallucination is an incentive problem, not a gap in knowledge.

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