What does the Audi A6 Avant's 'Quattro' system do?

I am interested in purchasing an Audi A6 Avant, but I am not familiar with the 'Quattro' system. Can someone explain its purpose and how it affects the car's performance?

The 'Quattro' system in the Audi A6 Avant is a type of all-wheel drive that uses a center differential to distribute power to all four wheels as needed. This improves traction and stability, especially in severe weather conditions such as rain or snow.