I have a 2001 Ford Expedition, Eddie Bauer with AWD. The owner's manual isn't very clear and I'm not a tech so I could use a simple explanation how how my AWD works and how it's different than the 4-wheel drive setting. Which is better on snowy roads. I never off-road, it's a company vehicle.
I was never good at explaining things so I added a link too :)
In 4x4 all tires rotate evenly. This puts alot of stress on the drivetrain when making turns on dry since for example when you make a left turn the wheels on the left side will have to rotate less than the ones on the right. When turning on dry in 4x4 the left tire actually skips on the ground to make the turn since it is forced to turn at the same revolution as the tires on the right. and vice versa when making a right turn.
AWD compensates and does not lock all 4 tires and allows the various wheels to move at different revolotions.