Dungeon Master

The Dungeon Master (DM) is the story-teller, facilitator, rule-master, and pretty much God at the gaming table. He or she has the final say at the table. The DM tends to put a lot more planning into the sessions than a player would as he or she is the one who prepares things in advance or sometimes flies by the seat of his or her pants.

While the DM doesn't actually play, he or she uses NPCs or Non-Player Characters. In a sense, the DM does get to play, but it's done with many NPCs throughout the story. For example, the DM becomes shopkeepers, guards, Mayors, etc.