The GM works as director, to keep the character interaction high. The model is concerned with conflict, characterisation, portrayal, and the like. The GM acts as a referee, insuring fairness. The model concentrates on fairness and competition. Most often system-centered.
Concentration is on details, coherency, and general believablity.
Here, players use their characters as facades, through which they can interact with the other players in new and interesting ways, and the GM strives to create unique settings for interaction. Concentration is on interaction, humor, and player bonding. The GM tries to create situations in which the players can relive themselves of the stresses of everyday life, in whatever manner the players do this. Focus on creating interest, escape, and the release of player tension. The center here is fun, while the other models are really usually aiming for satisfaction.