Ok, listen up. This is one of the best games ever made. There are 3 races, Terran (human), Protoss (advanced alien), Zerg (sacrifical alien).  You choose your race and battle in an area where you will find crystals and gas.  You must build up your army and FIGHT TO THE DEATH!!! It has great online play, the best of the best. If you like this game, I suggest you try WarCraft!