The full list of staff can be found at the staff page
Admins deal mostly with organizational and general website matters, making sure everything runs smoothly. All important decisions and changes have to pass their approval first.
Moderators look after the forum and members, moving / locking / deleting threads and posts when necessary.
Staff work on site content - featured bands, reviews, interviews, news, releases and other such things.
You can tell which position a person has by looking at their profile, or looking at the letter in their gender sign.