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.
The clock spring is a winding of metal that allows for a rotating steering wheel to have an electrical connection for mounted controls and air bags.
How to Restore a Car's Steering Wheel by ChrisFix
Early Modes of Steering
Numerous designs for methods of steering a vehicle existed before the steering wheel as well as while it was becoming mainstream. Crank handles are a common example, using similar methods for mechanically changing the direction of the wheels, but with a different method of allowing the driver to hold it.
Unusual/Experimental Steering Methods
Although they usually don't make it past the concept car stage, many designers have tried to reinvent the steering wheel.
Wrist Twist Steering System 1965 Promotional Video
This is a film made by Ford Motor Company from 1965, demonstrating an experimental device that aimed to replace the steering wheel, called the Wrist Twist steering control.