A hollow band of rubber, often reinforced with fibers of other material, fitted around the outer edge of a vehicle's wheel and filled with compressed air.

Tires are the primary means of pushing a car along by applying the force of friction. To give the car maximum push, tires must grip the surface of streets and highways with the powerful force of "static friction".

As well as maximizing static friction, tires must minimize another kind of friction, called rolling resistance. Rolling resistance happens because tires are repeatedly squeezed underneath where the wheels press on them and stretched at the top when wheels release them.

All that stretching and squeezing wastes energy which could be used to go forward.