All Wheel Drive is a totally different animal in that the center has a differential that shifts power between the front and rear as needed plus the differentials in the axles have traction devices to allow power to switch between the two wheels on that axle so that the wheels can turn at different speeds which allow them to be used on the highway. Think Subaru, Audi, etc. This system is not considered by many to be true 4wheel drive because at any one time power may not be available to one of the wheels and therefore does not provide the maximum traction you would get with having them locked but you can steer the thing.
Our Toyota Highlander is like that. However, it does have a real 4x4 that you can lock in for tough spots. It disengages at about 25 mph, though, and you're back to AWD.
