Module 1 · Foundations

Lesson 1What an LLM Actually Is

5 topics11 min readTopics 1–5

Welcome to Module 1: Foundations. Five topics, and they are load-bearing walls — what an LLM is, how it learns, what it actually reads, and what it can see at any moment. Everything in the sixteen lessons after this one stands on them, so this lesson is worth reading slowly even if parts feel familiar.

In this lesson

  1. 1LLM Basicsthe autocomplete that ate the internetForget "artificial intelligence" for a second. An LLM (Large Language Model) is, at its core, a very powerful autocomplete. You've used…2 min
  2. 2How AI Models Workknobs, guesses, and correctionsHow does a model learn to predict the next word? Three ideas: Idea 1: Everything is numbers. Computers can't process words. So words get…3 min
  3. 3Tokensthe model's alphabetHere's something surprising: models don't read words. They don't read letters either. They read tokens — chunks of text that sit somewhere…2 min
  4. 4Tokenizationhow the chunks get chosenSo who decides that "unbelievable" splits into un/believ/able? A separate small program called the tokenizer, built before the model is…2 min
  5. 5Context Windowsthe model's working memoryThe context window is the maximum number of tokens a model can look at at once — your entire conversation, system prompt, documents, and…3 min

Start with Topic 1: LLM Basics, or browse all 90 topics.