The DM portrays nonplayer characters, makes up the story setting for the other players, and serves as a referee.
( DM, or GM, or Game Master): The referee who creates the dungeon, provides the setting for the game, and handles all monsters encountered. (D&D 1)
The original term for the player who 'directs' the game. Another word for Games Master, Storyteller, Keeper, Director etc.
Dungeon Master is the first 3D realtime action computer role-playing game, published in 1987 for the Atari ST by FTL Games. It went on to become the ST's best selling product of all time, reaching an astounding market penetration of more than 50% of the Atari STs ever sold.
In the Dungeons & Dragons (D&D) role-playing game, the Dungeon Master (abbreviated as DM) is a selected player who describes the game to the other players. In effect, the Dungeon Master creates the entire world and allows the players (the DM is usually not described as a player) to interact with that world.