A hands-on tutorial you can run for free in Google Colab.
Run it yourself: open foundation_instruct_chat_tutorial.ipynb in Google Colab and run every cell top to bottom. It uses the SmolLM2-135M family — small enough for a free CPU runtime, no GPU needed.
Why this confuses everyone
People say "LLM," "GPT," "an AI model," and "ChatGPT" as if they were the same thing. They aren't. There's a ladder of training stages between "a model that read the internet" and "an assistant you can chat with," and the words foundation, instruct, and chat mark the rungs.
The cleanest way to feel the difference is to do something deliberately unfair: ask the exact same question to three versions of the same model family and watch how differently they behave. Our question is deliberately boring so the behavior stands out:
