What is Quattro and how does it improve the performance of Audi A5?

I've heard a lot about Quattro in Audi cars, but I'm not sure how it works or why it's beneficial. Can someone explain the technical details to me?

Quattro is Audi's all-wheel drive system that distributes power to all four wheels for improved traction and handling. It uses sophisticated sensors and electronic control units to continuously adjust power distribution, giving you maximum grip and control on any road surface.