well, "what" it use to make general questions, while "which" it use to make specific questions, for example, what kind of music do you like it? (that is a general question about music) which rock band do you like it? (that is a specifit question about music, because we are talking about only one kind of music)

"Which" is usually talking about choosing from a list of options. Ex: Which one of these should I eat, the apple or the orange? "What" offers limitless options. Ex: What should I eat? You decide.