In most forums, classes are when you pretend to learn about magical school subjects. That is not what Potterhead's classes are. Now, I'm not saying we won't ever have something like that. I actually ether like them. It's just that until I get a few mods to help me out, it's not practical.
What the classes are, are discussions. Anybody can talk about various subjects in the seperate forum for example, in the a Flying Class, there might be a topic about the Olympics or even about the Super Bowl. There might be clubs you can join and even contests. It's all up to you. So head on over to whichever PHF class interests you most.