What is the purpose of the Audi A3's start-stop system?

I've noticed that when I come to a stop, the engine of my Audi A3 turns off and then starts back up when I press the accelerator. What is the purpose of this feature and how does it work?

The start-stop system in the Audi A3 helps to conserve fuel and reduce emissions by automatically turning off the engine when the car is at a complete stop. This is especially useful in city driving and heavy traffic.

The start-stop system works by using sensors to detect when the car is not moving and automatically turns off the engine. When the driver releases the brake pedal, the engine restarts seamlessly.