What Is ChatGPT Doing… and Why Does It Work?

Stephen Wolfram's February 2023 long-form explainer — the most-shared single technical introduction to ChatGPT in the model's early months. He walks readers, with very little assumed background, through the entire stack: probability distributions over next tokens, embeddings, attention and transformers, training and reinforcement learning from human feedback, the role of model size, why language has computational structure that makes this possible at all, and where computational irreducibility limits how much we'll ever "understand" what's happening inside the model.