Starcraft is a computer game with 3 different species, the Zerg, the Terran, and the Protoss. They wage war across 3 different tilesets if you have the regular version of starcraft, and 6 different tilesets if you have the Starcraft Expansion: Brood War. You can play over the internet using battle.net™. The Zerg are carniverous aliens who live to kill. The Terran are very advanced humans who are trying to save thier home planet, Earth (yeah i know i have never heard of it either). The protoss are an advanced alien breed, who are protecting their home plane, Aiur. Check out the units for each breed here.