What does the Audi A1's start-stop system do and how does it work?

I've heard that the Audi A1 has a start-stop system but I'm not sure what it does or how it works. Can someone explain it to me?

The start-stop system in the Audi A1 automatically shuts off the engine when the vehicle comes to a complete stop. This helps to save fuel and reduce emissions. When the driver releases the brake, the engine restarts. Make sure to keep your foot on the brake while stopped to ensure the system works smoothly.