How does the Audi A6 Advanced Key system work?

I have heard that the Audi A6 has an advanced key system, but I am not sure how it works. Can someone provide a detailed explanation?

The Audi A6 Advanced Key system allows you to lock and unlock your car without having to take the key out of your pocket or bag. It works by using a sensor on the door handle to detect when the key is near.

Not only does the advanced key system make it easier to access your car, but it also allows you to start the engine without having to insert the key into the ignition. Just press the start button to turn on your car.

One of the key advantages of the advanced key system is that it can also be used as a safety feature. If you accidentally leave your key inside the car, the doors will not lock and you will be notified.