I can tell you how to use it but not how it works or how to maintain it -
First, you can switch to 4x4 while moving forward, but never, ever, ever turn on the 4WD while the tires are spinning (Like, if you're stuck in mud or sand or snow) - it will probably destroy your transfer case, along with other expensive parts. Firmly apply the brakes before turnin the switch to 4x4 high or low if you are stuck.
There is nothing automatic about the system - the knob on the dash turns it on or off, and when its on, it's on.
Both the front and rear have differentials, putting it in 4WD guarantees that at least one wheel on each end will be spinning, and in good traction, power will go equally to all four wheels
Don't use 4x4 high or low on dry pavement - you will wear out tires quickly, among other things
To put it in 4x4 Low, you have to stop, put the selector switch in 4x4 low, put the transmission in neutral, and apply the brake, and dont move until the 4x4 low light is on