How does the Audi A4's self-driving feature work?

I've heard that the Audi A4 comes with a feature that allows it to drive itself in certain situations. How does this feature work, and is it reliable?

The self-driving feature on the Audi A4, known as adaptive cruise control, uses a combination of sensors and cameras to constantly monitor the road and adjust the car's speed to maintain a safe distance from the car in front of it. It also has the ability to steer the car within its lane.