You must research new technologies, explore the galaxy, settle new planets and ultimately negotiate with and defeat alien races to rule the galaxy as your own. The game itself is played in real time at one of three speed settings. You can also pause the action to issue orders. There are set piece scenarios as well as campaigns played from the perspective of three different races. And while that sounds good, the races have identical technology trees and only have a few small differences in what they can and cannot do.
Campaigns are also misnamed.
They aren't campaigns in the sense of linked missions. Rather, they are the game itself with random events. Events might require you to save a ship from an enemy, root out pirates, etc. Completing these missions is mostly optional but doing so nets you various benefits in the form of money, technology, or what have you. Combat takes place both in space and on planets.