I frequently get asked questions about various 4 wheel drive system on Toyota products. In the past, I replied on an individual basis. Finally, I wrote a fairly comprehensive piece on it but felt it was too long to post here. I have broken this up into four parts. The first is a list of terms and definitions. Next is an explanation of the Active-Track system on the Sequoia, Land Cruiser and 4Runner. Next is conventional 4WD systems like the Tundra and Tacoma have. Finally is a discussion of the AWD of the Highlander and RAV4.
I hope this is helpful.