In a post apocalyptic world, nothing is more important than to survive. There are gangs everywhere and they won't let you alone. They want you to give your valuables to them or you will be facing their justice. At least, that is what they call it, but everyone knew that those gangs are pure evil.
You will start with just one car, but eventually you an afford other vehicles as you are earning based on the distance you traveled and the enemy you destroyed. Try to upgrade the vehicles, so that it would be helpful in the fight against the gang.