Haha well there are probably other fleet members who know far more than i do, but there is a wiki
here.
You have the two sides (Republic and Sith)
Each has two force using classes, then a smuggler/bounty hunter, and Trooper/Agent. (Four classes in total)
Each class can choose a specialisation (i guess similar to wow talent trees).
It seems you can get your own ship eventually, and even a companion (not sure what benefits these provide)
I'm not sure how much detail has been released on things like character customisation etc, but I expect it will be good (at least I hope it is given the limited race/class combinations they are starting with).
*tries to think of more stuff...*