What does the Quattro system in Audi cars do?

I've heard about the Quattro system in Audi cars, but I'm not sure exactly what it does. Can someone explain it to me and how it affects the driving experience?

The Quattro system is an all-wheel drive system that distributes power to all four wheels, providing better traction and control in all road conditions.

The Quattro system also helps with fuel efficiency by only sending power to the wheels that need it, reducing unnecessary energy usage.

In my experience, the Quattro system has greatly improved handling and stability, especially in adverse weather conditions like rain or snow.