The Game Moderator, Game Master, God Mobian (as Taniciusfox claims it to mean in his games), or simply, GM, is the person responsible for the management of a game.
GMs craft the rules, the map, and every aspect of the world. They also control any NPCs. They are basically limitless in terms of power in the games they run, able to override player actions, alter the rules of the world at whim, and even ban troublesome players (although particularly meddlesome GMs can be met with substantial backlash).
Games are generally run by a single GM, although in the case of IOT V, it was managed by a team. GMs have occasionally retired mid-game and passed responsibility to another person to continue management, so as to avoid its closing.
For a list of IOT GMs, see Category:Game moderators.