quattro is a permanent all-wheel drive system. If the wheels on one axle of the vehicle lose grip on the road and threaten to spin, wheel-selective torque control distributes the drive force through the transfer case and hydraulic multi-plate clutch to the axle or individual wheel with the better grip.
With quattro you will experience directional stability, dynamism and agility as never before, while counteracting over- and understeer without any problems. The benefits are clear: better traction and thus improved acceleration as well as greater safety thanks to more balanced cornering forces.
Article source: www.audi.com