Aurora is really more like a tool than a "game"
It is designed to simulate the history of space empires, and provides many tools that help with this simulation.
It is also designed so that more than one player could play it.
In effect, spacemaster works a lot like the "dungeonmaster" of Dungeons and Dragons...it's a person that has almost complete control of the universe, who sets it up a certain way for players. If you're not familiar with Dungeons and Dragons, imagine it a bit like a referee or umpire. he decides things like "Okay, in this universe, it's 2091, and there's a robot empire and a mutant empire and a human empire. the human empire has advanced tech but no ships, the robot empire has many ships but they are on titan which is a bad planet for mineral resources, and the mutant empire has many worlds of high populations but very poor tech and very few ships..." ect.
Most people don't use aurora in this way but the functionality is there.
For a one player game, spacemaster mode is usually used to "set up" the game, create a bunch of ships, explore a few systems, establish big colonies, then the player turns on single player mode and actually starts playing. Unlike many games, there is no real way to "win" aurora so this isn't exactly cheating...I use spacemaster mode in my games to create threats for my civilization to fight...for example, I simulate revolutions on outlying colonies or the discovery of hostile alien races in the depths of space.
It's mostly used to set up things. I like playing scenarios where I start out with literally nothing, 2000's era technology with no shipyards and just some conventional industry and a few (bad) scientists and slllloooooooowly expand into space, but a lot of players want to start out as, say, the highly advanced Voldrakni Collective with fleets of shielded plasma warships. This is how you'd create such a thing.