u/Some-Nerve-9502

So I've been seeing people saying that they use Anki or Quizlet to create flashcards to help them with A level revision. I want to do this, but I really do not know what to put on the flashcards, like what information do you put, definitions...? I really need help to understand what you guys put on your flashcards to make them useful for revision. I'd really appreciate your help.