Mini-Modding is the doing things that only a moderator/administrator would usually do. It consists of things as simple as telling someone not to break a rule.
Moderators and administrators alike also tend to dislike Mini-mods, since they see them as irritating. It is generally not recommended to Mini-Mod, because you actually do not have the ability to ban the user, and you may provoke someone to break the rules even more. If someone is braking the rules, simply flag them or ask a moderator if they can help out in the chat.