On this site, there are five people who moderate, three administrators (Carla, Arthur and LadyCFII) and two moderators (Gamey and eyeshigh). Gamey and eyeshigh were chosen as moderators for the Fun Stuff area so that the administrators could concentrate more on the forums dedicated to the games as well as their work on VV3. In general, moderators are always well-known and well-respected adult users who have been active members for quite a while.
Moderators enforce the rules. They generally go through the posts, editing them as needed. Inappropriate content would be deleted, way off-topic posts would be deleted, certain comments edited to include Spoiler tags, threads which belong in a different area in the forums would be moved, etc. Those are just some examples I've seen done on this site.