What is the purpose of the Audi A1's engine start-stop system?

I recently purchased an Audi A1 and have noticed a random button labeled 'auto start-stop' next to the gear shift. What does this do exactly? Does it save fuel? And how does it work?

The auto start-stop system on the Audi A1 is designed to save fuel by automatically shutting off the engine when the car is stationary, such as at a stop light or in bumper-to-bumper traffic. This feature can also reduce emissions and extend the life of the engine. However, it may take some getting used to as the engine will restart as soon as you release the brake. But don't worry, it's completely normal and the system is very responsive.

The auto start-stop feature on the Audi A1 can also be manually turned off if desired. Simply press the 'auto start-stop' button to disable it. This may be useful in situations where you want to keep the engine running, such as when driving through a car wash or when using certain accessories.