You might not care. That be allright. If you aim to misbehave, this wiki be shiny for you.
Here's how it is...
Earth-that-was got used up.
We moved out -- terraformed and colonized hundreds of new earths; some, rich and flush with the new technologies; some, not so much. The central planets -- them as formed the Alliance -- decided all the planets had to join under their rule.
There was some disagreement on that point.
After the Unification War, many of the Independents who had fought and lost drifted to the edges of civilization, far from Alliance control. Out here, people struggle to get by with the most basic of technologies. A ship will bring you work; a gun will help you keep it.
A captain's goal is simple: find crew, find a job... keep flying.
This wiki is an encyclopedia of the Firefly 'verse (created by Joss Whedon), intended both as a resource to fans of the television show (and upcoming movie) and to show people what a cool show Firefly is. http://www.fireflywiki.org/Firefly/HomePage