If you take a look at the FAQ, it shows you what you need.
For quick information:
Moderator: Looks after a certain section(s) of PC
Super Moderator: Looks after all the section of PC
Assistant Admin: Provides assistance to the Administrators and Staff Admins, and have limited Admin Control Panel Access
Admin/Staff Admin: Looks after all of PC and has admin control panel access.
Hope this helps...
Edit: beaten...