What is the operation of the Audi A5's Auto Stop-Start feature?

I keep seeing this mode on my Audi A5 but have no idea how it works. Can anyone explain it to me?

The Auto Stop-Start feature in the Audi A5's engine automatically turns off the engine when the vehicle is idling, such as at a stop light. This helps to reduce emissions and improve fuel efficiency. However, it can be disabled if preferred.

This feature can also be temporarily deactivated by pressing the ESP button on the center console, and then holding it down for 3 seconds until the symbol on the instrument cluster illuminates. This can be useful if driving in heavy traffic or stop-and-go situations.