Here is a nice video with CGI that shows the premise of the X-drive system in many BMW models. The X6 is the only exception. The system transfers power from front to rear as needed.
It differs from many other manufacturers in the front drive application and location of the system. It is not symmetrical and the differences in the length of the drive axles can create a front “torque ” steer, though not significant.
Watch carefully and realize there is a hiccup in the system on the 5er wagon when it is on the incline with one side on ice….
There are some great safety and performance advantages to all-wheel drive and especially in snow and inclement weather, drifting anyone?