What is the auto hold feature in the Audi A5?

I just bought an Audi A5 and noticed a button that says auto hold. Can someone explain what this feature does?

Auto hold is a useful feature that allows you to stop and hold your car in place without having to keep your foot on the brake pedal. It's great for heavy traffic or when waiting at a long traffic light. It's easy to use, just press the button and it automatically activates when you come to a complete stop.