How do large language models like ChatGPT actually learn and generate text?

Large language models like ChatGPT learn by reading and rereading a huge amount of text, just like how you might learn to speak by listening to your family talk every day.

Imagine you're learning to write stories by reading hundreds of books. You notice that certain words often go together, like "the" followed by "cat," or "happy" before "ending." The model does something similar: it looks at word patterns and learns how sentences usually flow.

The model reads a lot of text, millions of sentences, and tries to guess what word comes next. It’s like playing a game where you try to finish someone else's sentence. If it guesses right, it gets a little reward; if not, it tries again. Over time, it becomes really good at predicting the next word.

When the model wants to write something new, it starts with a few words and keeps guessing what comes next, like building a sentence one block at a time. It uses all the patterns it learned before, so its writing sounds natural and makes sense, just like how you might tell a story after listening to many others.

It’s not magic, it's just really smart practice!