What is the Quattro system in Audi A4 and how does it work?

I've heard about the Quattro system in Audi A4, but I don't fully understand what it does and how it works. Can someone explain it to me in simple terms?

The Quattro system is Audi's all-wheel-drive system, meaning power is distributed to all four wheels for improved traction and handling. It works by using a center differential to send power to the front and rear axles, and can adjust the amount of power sent to each wheel based on driving conditions.