What is the difference between quattro and all-wheel drive in the Audi A6?

I am planning to purchase an Audi A6, but I am not sure what the difference is between their quattro and all-wheel drive systems. Can someone provide a technical explanation?

The main difference between quattro and all-wheel drive in the Audi A6 is the distribution of power between the front and rear axles. Quattro is a permanent all-wheel drive system that sends power to all four wheels at all times, while all-wheel drive is a part-time system that only sends power to the rear wheels when needed. Quattro provides better handling and traction in all weather conditions, while all-wheel drive is more fuel efficient and only activates when necessary.