Your faction will modify the menus' visual themes, and everything you do in the game will earn points for your faction. Assuming you're online, when you first start Mortal Kombat X you'll be asked to choose one out of five factions associated with groups in the game's fiction: White Lotus, Brotherhood of Shadow, Black Dragon, Special Forces, or Lin Kuei. It also sounds like the best rewards will come from Mortal Kombat X's greater, cross-platform multiplayer Faction War mode.
NetherRealm is still a little vague about what exactly you'll be able to spend these points on, but cosmetic changes to characters is one example. These aren't merely fun, almost puzzle-like elements to introduce to a fighting game-they’re also a great way to force and teach a lone player to discover each fighter's movelist. The conditions I saw were focused on winning rounds while using certain moves. Each level in the tower has some kind of environmental twist-I saw one where bombs were falling from the sky, another where I had to dodge roving laser traps-and an extra condition that will earn you more points.