In Full Time drive in the tightest circle you can drive in a parking lot, it will feel normal, in Part Time do the same and you'll feel the steering wheel buck a little bit.
With Full Time you can drive on dry pavement and not mess anything up, in Part Time you can only use it on slippery loose surfaces or you'll have some driveline stuff break on you.
Just remember FUll Time you can use whenever you feel like, Part Time you can only use part of the time.
Hope this helps