Starcraft is a video game where you get to control different types of aliens called "units". You can choose to control one of three different factions - the Terrans, the Zerg, or the Protoss. Each faction has different kinds of units that you can command, like soldiers, tanks, or spaceships. You can use your units to do different things like build buildings, gather resources, and fight battles against your opponents. The goal of the game is to defeat your opponents by destroying their units and buildings.