How is the AWD controlled on my 96 Blazer?

If its 4 wheel drive there is a encoder motor on the transfer case that makes the gear changes. All wheel drive vehicles like the Astro van have a clutch assy in the transfer case similar to a posi rear end clutch pack that allows some slip to reduce driveline binding when turning corners.

I am an electromechanical person that is trying to understand why I had to pay some yahoo a hundred bucks to spend 2 minutes pulling me out of a snow bank when the drivers side wheels were still on pavement? the right rear wheel was definitely spinning, so why wasn't the power diverted to the wheels on the pavement. I wish the hell I had 4wd drive like on my old jeep, I would have put it in 4wd low and been gone. My opinion is that AWD sucks!

If your vehicle has all wheel drive that dosen't meen all of them will be under power all the time. The front axle will never have posi or limited slip like a rear end might. This is to prevent the steering wheel from snapping your wrists when one tire grabs and the other dosen't. So the front wheels will only move the vehicle when both tires have traction. The rear end may or may not have positraction or limited slip (optional). If the rear end is open or no posi it will also not move the vehicle if both tires don't have traction. So we can assume both of your left tires were not spinning and both the right were spinning. Some vehicles have traction control systems which will use the abs system wheel speed sensors to detect spinning wheels Traction control works by applying the brakes to the spinning wheel forcing tourque to the other wheel and hopefully moving the vehicle. If you have traction control it is turned off or not working or the remaining tires on the pavement could not get enough of a bite to get you out.