Their job is to stay on top of the usual exceptional behavior you will find on the internet: Spam, vandalism, rudeness/harassment, vote manipulation, sockpuppet

Their job is to stay on top of the usual exceptional behavior you will find on the internet: Spam, vandalism, rudeness/harassment, vote manipulation, sockpuppetry, user bans, ban disputes and so on. Contrary to popular belief, moderators have no special impact on questions getting closed (or downvoted) - that's handled by the "normal" users.