Well, let's see. The Universe edition includes all previously-released versions and expansions, so you get basically the full DW experience. You can choose from several different "campaigns" taking place at different points in the universe's timeline. You can choose to play as a pirate faction in most of these campaigns if you so desire, shaking down weak empires and poorly-defended worlds for money and supplies.
As a normal empire, you have two primary types of ships: State-owned and Civilian. State-owned ships are your warships, your scouts, your construction vessels, and space stations. You can give them orders, you can decide when to build such things and how many to build, and you pay out of the empire's pocket for each one. Civilian vessels such as freighters, passenger transports, mining vessels, run around and do their own thing. You cannot directly control them in any way, nor can you order them to be built. However, since they are built at your government-owned shipyards, and they are vital for keeping an empire of any size moving smoothly, the construction of civilian vessels actually puts money in your pocket.
I already said there were more than a dozen races. Each of them have a type (humanoid, insectoid, etc), a preferred planet type, special victory conditions to pursue, racial bonuses, and bonuses from certain resources. Many of them also have unique techs, special buildings, or special government types. And speaking of government types, each one has its own bonuses and penalties to various aspects of your empire's abilities. You can change government types during gameplay, though you typically go through a period of unrest by doing so and unhappy worlds might decide to break off and become independent.
And then there's independent empires! Not only do you have the other main factions running around the galaxy, trying to win the game, but there are also dozens of tiny empires scattered all over the place. Sometimes they can be absorbed peacefully into your own empire, other times you will have to conquer them. And if you enable the appropriate settings, these small empires can eventually grow on their own, becoming new main factions that will also attempt to win the game! Pirates can do this as well.
Would you like to know more? There's still a lot to cover but I'd like to know what to focus on