Definitions for "ALL WHEEL DRIVE"
Keywords:  awd, suvs, torque, wheel, road
All four wheels are driven by the engine. AWD systems are superior to 4WD as AWD can be used under any road conditions.
A vehicle drivetrain with a center differential having all four wheels under power at all times
Taken literally AWD means all four wheels can be driven, but there is some ambiguity as to just what "driven" means. If a centre diff' is used between the front and rear axles then all wheels share equal torque (unless one slips and an LSD or diff' lock takes over). A cheaper arrangement is to drive one axle via a viscous coupling or similar. In this case one axle receives no torque until the other axle slips - is this all wheel drive? Debatable.