You basically drive around shooting NPC cars and various critters, and collect their loot. The problem is, the combat is really basic. There is no front/side/rear armor, it's just one bar. There doesn't seem to be much strategy to fighting, other than trying to stay on someone's tail.
It's action combat, but it's kinda MMO-esque. For instance, I have a mortar on my car. If I have something targetted, and it's in range anywhere around my car, I shoot it and it may hit or may miss, it's a die roll.
There are front and rear mounted weapons as well, and you have to have the target in your front/rear arc for these. I don't really see if that is going to make combat compelling enough to make anyone want to play this for more than 10 hours.