This is a way of marking territory if they are rubbing the sides of their faces on the object. Cats have scent glands around their lips and on their chins. The facial pheromones that they mark with are signals of a happy or calm cat to other cats.
The part that simultaneously enables the axle to flex while transmitting the driving force is called a drive axle joint, and is also known as a constant velocity (or CV) joint. The CV Boot is a ribbed, rubber flexible boot that keeps water and dirt out of the joint and the special grease inside the joint.
VIN is an acronym for vehicle identification number. It is a serial number composed of numbers and letters. Each vehicle has a unique identification number that can be used by the Department of Motor Vehicles -- aka, the DMV-- to identify cars and other motor vehicles. The DMV is a government agency that handles regulations on land vehicles.