Game+ is a game feature that allows a character who has beaten the game to play again, retaining some advantage that zie has earned, or allowing the player to start at a plot-branch point and travel the "road not taken". The first game with this feature that I know of was Chrono Trigger.
A plot is a sequence of events that raise the level of dramatic tension as the player progresses and becomes emotionally involved with the game, then satisfies this tension with a resolution that (hopefully) prevents the player from being resentful that there isn't any more game.
A plot can be linear or branching, and may have one ending or a multitude of possible endings.
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