Its only on Ati video cards. Its when you have 2 of the same video cards hooked together to improve your frames per second (fps) in game. However, not to many games are compatible with crossfire, and you will be forced to only use one card instead of two. Crossfire is the same as nvidia's SLi, only but SLi is better because its more "thought out" and doesn't have as many bugs in it.
