Aside from watching the Magnus documentary about a younger Magnus while I was in high school, I have almost no knowledge about competitive chess. What sorts of

Aside from watching the Magnus documentary about a younger Magnus while I was in high school, I have almost no knowledge about competitive chess. What sorts of things do chess players engage in during the course of the six months leading up to a match? Is there something that they're trying to remember or a video that they're studying (what would they be looking for)? From the beginning, I was under the impression that they might be played at any moment. This sounds like a really difficult situation.