Here's how the steering column works to turn the wheels on your car.
The steering column connects the steering wheel to the rack. It also houses the airbag, controls for turn signals, cruise control, audio, wipers, ignition switch and steering lock, all of which are discussed in this video.
The bottom of the steering column is splined where it joins the intermediate steering shaft into the rack. A universal joint allows it to be mounted offset to the rack's pinon centerline.
Further up the shaft, is a collapsible portion that telescopes after a certain amount of force is applied. This prevents the steering wheel from being pushed up into The drivers face during a severe collision.
The steering lock consists of a tab that sticks out and engages a hole on the column, similar to a door lock. The mechanism disengages when a key is inserted and rotated, allowing the wheel to spin freely.
The ignition lock consists of a tumbler, the starter switch, a key detection switch and a lockout solenoid, all to ensure the off, acc, on and start positions of the key work safely.
Next up there's the turn signals, that use a cam-tongue mechanism that sticks into a rotating collar on the shaft. This allows mechanical self cancellation of the turn signal.
Finally there's a clock spring that allows 5 rotations of the steering wheel, while preventing tangling of the airbag and cruise wires. The steering wheel itself is a steel ring padded with colored foam, or is sometimes leather stitched.
This was performed on a 2001 Toyota Corolla.