How is the Audi A4's Quattro all-wheel drive different from other all-wheel drive systems?

I've heard that the Audi A4 has a unique all-wheel drive system called Quattro, but I'm not sure how it differs from other all-wheel drive systems. Can anyone explain?

Quattro is Audi's trademarked all-wheel drive system that distributes power to all four wheels for superior traction and control. Unlike some other systems, Quattro is always active and monitors wheel slip to adjust power distribution in real time.

Quattro also uses a center differential to distribute power between the front and rear axles, allowing for a balanced distribution that enhances handling and stability. Other all-wheel drive systems may use a simpler and less effective transfer case.