The host of a game (or just you if you're playing against the computer) can set a few options, including starting credits and beginning and end tech levels. Official maps have anywhere from 8 planets to the full 43, and can therefore take anywhere from a few hours to days or weeks to complete. The ultimate goal is to control every planet on a given map.
The meat-and-potatoes of the game, Galactic Conquest pits the Empire and Rebellion against each other in interplanetary warfare.
