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.