Gamemaster
A gamemaster (GM; also known as game master, game manager, game moderator or referee) is a person who acts as an organizer, officiant for questions regarding rules, arbitrator, and moderator for a multiplayer role-playing game. They are most common in co-operative games in which players work together and are less common in competitive games in which players oppose each other. The act performed by a gamemaster is sometimes referred to as "Gamemastering" or simply "GM'ing".
The role of a gamemaster in a traditional role-playing game is to weave the other participants' player-character stories together, control the non-player aspects of the game, create environments in which the players can interact, and solve any player disputes. The basic role of the gamemaster is the same in almost all traditional role-playing games, although differing rule sets make the specific duties of the gamemaster unique to that system.
The role of a gamemaster in an online game is to enforce the game's rules and provide general customer service. Also, unlike gamemasters in traditional role-playing games, gamemasters for online games in some cases are paid employees.