Game Master

A Game Master (also known as a "GM") is a person who acts as an organizer, officiant regarding rules, arbitrator, and moderator for a tabletop role-playing game.

The role of a Game Master is to weave the other player-characters' stories together, control the non-player characters of the game, create environments in which the players can interact, solve any player disputes, and create worthy adversaries for their players. A Game Master will sometimes utilize a helpful "GM screen" that keeps a host of useful pieces of information right at the GM's fingertips during gaming sessions.

The act performed by a Game Master is sometimes referred to as "Game Mastering" or simply "GMing".