Game Master Edit
AKA Dungeon Master; Referee; Narrator, ETC
The Game Master is role in a role playing game. While the players create their character, that character's background and dictate the character's reactions within the context of the story, the Game Master provides the rest of the story.
The Game Master creates a story line, with people, places, things and events germane to that story line, then he describes the people, places, things and events as the characters encounter them.
In a Star Trek Role Playing Game, much of the background is already created, allowing the GM to focus his creative energies on making up strange new worlds and amusing characters.
A specific story may be called a scenario, an adventure or an episode depending on the context.
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