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.
Ships include a wide array of types and sizes and you can customize the weaponry and abilities to create your own special types, upgrade existing ships and tanks, etc. It's very flexible, you can even buy surplus ships and tanks on an open market. But this flexibility adds a lot of complexity too, perhaps more than is a good thing. Ultimately the game system has good points and bad ones. The basic real time game engine is pretty good though the 3D battles are very difficult to adequately control.