OpenAI Founding member Karpathy’s 3-Hour Masterclass Is the Internet’s Best LLM Explainer — And It’s Free

This weekend, I sat down to watch Karpathy’s 3-hour deep dive into how large language models like ChatGPT are trained — and it turned out to be absolutely worth every minute. What surprised me most? It’s not just for AI experts.

Karpathy explains everything in a simple, clear way that anyone can follow — even if you're new to machine learning.
If you've ever wondered how AI actually works, this is the one video you shouldn't miss. It's insightful, beginner-friendly, and a perfect weekend watch for anyone curious about the future of technology."

From tokenization and attention mechanisms to model training and inference tricks — this isn’t just a talk. It’s the ultimate roadmap to understanding large language models.

Here’s how AI like ChatGPT is actually trained — in three essential stages:

1. Pre-training:

The model starts by learning from massive amounts of internet text — books, articles, code, Reddit posts — to build a general sense of how language works.

2. Supervised Fine-Tuning:

Next, it’s taught to behave like a helpful assistant by studying high-quality, human-curated conversations. This gives it purpose and structure.

3. Reinforcement Learning (RLHF):

Finally, the model is rewarded for good answers through trial and error. It improves by figuring out which token sequences work best — sometimes even inventing clever reasoning strategies.

But it’s not perfect! Karpathy also dives into the “sharp edges”:

Hallucinations (making stuff up)
Trouble with basic tasks like counting or spelling
Dependence on prompting techniques to stay accurate

>> Tools, better prompts, and smarter training are all part of making LLMs more useful — and Karpathy’s breakdown shows exactly how it's happening.