There is the pre-training, where you passively read stuff from the web.

From there you go to RL training, where humans are grading model responses, or the AI is writing code to try to pass tests and learning how to get the tests to pass, etc. The RL phase is pretty important because it's not passive, and it can focus on the weaker areas of the model too, so you can actually train on a larger dataset than the sum of recorded human knowledge.