A spin-off is a game that has nothing to do with a certain series. Take the Pokemon series, for example. Usually, you're out to be a Pokemon Master by capturing every Pokemon that you possibly can, battling the Elite Four, and raising them all to level 100. Then they started coming out with games like Pokemon Ranger, Pokemon Puzzle Challenge, and Pokemon Snap!. As you may know, Pokemon Ranger, Pokemon Puzzle Challenge, and Pokemon Mystery Dungeon have nothing to do with capturing, battling the Elite Four, and raising them to level 100. Anymore questions? Just post here and I'll tell you more about what spin-offs are!