SQL for a Forum

Hey, I'm making a php forum, and I'm stuck a little...

For categorys, forums and threads, how would I get them in the right place using what SQL tables?

I really have no idea, I was thinking about the categorys name (ie The Zone) then it has the forum id's in a row called "forums". Then the forums have the names... but ah, I'm unsure.

Can anybody think how it'd work? Don't post any code I just need to know how to do it, what to put in tables...

Thanks.

Use a primary key on each of the rows and just create relationships based on the primary keys.

OK, I don't think I should do that with ID's then, just with names.

Thanks Tom.