The steering wheel is one of the three most important driver control devices in any vehicle, the others being the throttle and brake pedals. It allows the driver to direct the vehicle towards the left or right by changing the direction of the front wheels via the steering system.
The steering wheel often contains a button for the horn, and sometimes includes other controls like the radio's volume control or even traction control on some sportier vehicles. Many modern vehicles have an air bag stored in the center.
Pictured at the right is a steering wheel from a Ferrari which has many more controls than the average steering wheel. It allows many settings to be actively adjusted while driving the car.