How does AWD work?

Those links are the typical "transfer power from wheels that slip to wheels that grip" TV commercial information. The AWD system depends greatly on the type of transmission, manual vs automatic. The manual transmission has a viscous coupled center differntial giving 50/50 power to the front and back wheels (capable of approximately 80/20 or

20/80 depending on tire slippage). The front and rear differential are still slip type which means in the end only one front wheel and one rear wheel will get the power. A rear limited slip differential was available on some models. The automatic transmission uses a wet transfer clutch integrated in the transmission which supplies 90% power to front wheels and 10% to the back under normal conditions (this can change from 90/10 or 10/90 given certain conditions). I did hear somewhere that the newer subie autos changed the normal transfer ratio from 90/10 to 60/40, but am not sure on that one. The auto uses sensors on the each of the wheels to detect tire slip and adjust power transfer whereas the manual is purely mechanical. Over time the transfer clutch can wear out and fail to engage when front wheel slippage is detected (rendering your AWD vehicle a mere front wheel drive), I have also heard some stories of the transfer clutch binding and causing troubles with cornering.

In an open front or rear differential, torque is applied evenly to both sides, until one starts to slip. Then it becomes 100/0 in favor of the spinning side.

until one starts to slip.

.. but the torque is still applied equally. The spinning wheel gets essentially no torque and neither does the stationary wheel - otherwise you would be accelerating. By definition, an open diff always applies equal torque to both wheels. A locked diff or solid axle provides torque to each wheel in proportion to the traction.

I think you got me there.