What ChatGPT is actually doing when it answers you

It doesn't "understand" you. It does one thing, over and over: guess the next token, append it, guess again. Once that clicks, the weird behavior stops being mysterious: Tokens, not letters — that's why it can't count the r's in "strawberry". Meaning is geometry — words become vectors; "king" sits near "queen". Attention decides which earlier words matter for the next one. Pretraining makes a wild autocomplete; RLHF turns it into an assistant. Temperature is why the same prompt gives different answers. The context window is why it "forgets" — the oldest text literally falls off. Hallucination is the model doing its job (plausible text) where plausible ≠ true. Nine minutes, fully animated, no math required: Which of these surprised you the most when you first learned it?