How does the Audi A8's all-wheel drive improve traction and control?

I've heard that the Audi A8 has all-wheel drive, but I'm not sure how it works or what benefits it provides. Can someone explain it to me?

The Audi A8's all-wheel drive system constantly monitors all four wheels and adjusts power distribution to ensure optimal traction and control on all types of driving surfaces.

Having all-wheel drive on the Audi A8 means that you'll have better grip and handling in less than ideal weather conditions, such as rain or snow.