You start with your tiny little ragtag fleet of ships and have a whole sector to explore. You can trade and do merchant runs; you can act like a pirate and intercept convoys and raid stations; you can sign up with one of the major powers and fight in their wars; you can explore the outer reaches of the sector, bringing back lost tech from the previous wave of colonization; and you can even try to settle down somewhere and start up some colonies of your own, though the greater powers in the area may not like that if you start doing too well.

The real key attraction is the battles, which is space fleet combat interpreting WW2 naval principles. Ships are a blast to pilot and bigger fleet v fleet (or fleet v fleet+orbital station) engagements are a lot of fun to navigate, and the balance has gotten to the point where most ships are viable in some way, though you may have to try them out a bit before figuring out how to use them.