"What kind of ___?" is a way to ask for more details about something. For example, if someone tells you that they like hip-hop music, you can ask:

What kind of hip-hop?

You're asking to hear more details about the specific genre or style of music.

As another example, imagine that you're talking with a coworker about what food he likes to cook.

A: I do a lot of baking.

B: Baking? Really? What kind of baking? Like bread, or like cakes and cookies?