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What this video is about

Andrej Karpathy gives a deep, practical walkthrough of how large language models like ChatGPT are built. He covers the full training pipeline, from raw text data to a working model, and explains the key ideas behind pretraining, fine-tuning, and RLHF in plain language anyone can follow.

Key topics covered

The video explains how transformers learn to predict the next token, why scale matters so much, and how instruction-tuning turns a raw model into a helpful assistant. Karpathy also shares honest mental models for understanding what these models can and cannot do reliably.