The game is a simulator of the police chasing the player. You have to avoid the chase and not be arrested.
You drive a racing car driving around the city. If you hit some objects or crash into cars, the police will start chasing you. The more often you crash into something, the more wanted stars you will get.
The number of wanted stars = the number of police cars that will chase you.
To escape the chase, you can repaint and repair the car in the workshop.