.....One thing I'd like is an explanation of the difference between mods, supermods and admins since, from the perspective of an ordinary user, there is no obvious difference.
The wikipedia entry HERE should answer your question.
Basically a normal Mod is usually assigned an area of a forum to look after, a global or super Mod can look after the entire forum and an Admin is the Administrator who deals with the nuts and bolts of running the forum, and doesn't usually act as a Moderator, but can do if they wish.
I moderate on a different forum, and that is the setup we use, except that as a mod I have full access to the entire forum, but limited access to what I can do to a members account. A global mod has full access to everything, but holds a "arbiters" role in the event of a dispute between members and Mods and the Admins are purely the back room techies.