If you make someone moderator that means you give them the power to help manage the stream. Moderators approve posts and make sure everyone is following the rules. They can also delete comments and disapprove posts that seem to be violating the rules. However, if it seems like one of the people you gave mod to is abusing their mod, (meaning they edit un-nessecery things, delete things randomly, ban people for no reason) You, the owner of the stream, can remove their mod.