Stole this from another site, it's a good breakdown. I was looking for the Land Cruiser FT 4WD definition as I think the systems in the Land Cruiser and Limited Tacoma/4Runner are similar minus the differential locks in the Cruiser.
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"AWD, 4WD (part time), and Full-Time 4WD
AWD is a system in which each wheel can gain traction independent of the other wheels and their behavior. All wheels are capable of being driven simultaneously, spinning at different speeds, in all grip conditions. Power is sent through the center diff (often with a rear power bias) to each axle, which both contain limited slip differentials. If traction is lost on both axles, all four wheels will continue to receive power and turn regardless of the condition. No 4runner possesses this system. These are our Audi and Subaru friends.
Part Time 4WD system: When engaged, part-time 4WD system sends power 50:50 (front:rear) to each axle, and simultaneously to all 4 wheels. In the event of a loss in traction, power is sent to the wheel with the least resistance. If you have a loss of traction on each axle, power is sent to the wheel offering the least resistance (on each axle), meaning you're basically stuck. This is due to having open differentials on each axle. All 4WD 5th gen 4runners have open differentials on each axle. Only our 2WD friends get an LSD on the rear axle.
Im pretty sure most of us agree on these two systems and their differences, but if not, please chime in!
Now where things get confusing:
Full-Time 4WD is just like it says on the box. It’s what we have in the Limited. It’s the full-time version of what I’ve just described for our part time friends (specifically open differentials), but with a major distinction: The system employs a 40:60 torque split in most driving situations and alters that in response to slippage. In addition, if the front wheels are slipping while the vehicle is turning, the center differential changes the torque split to 30:70. If the rear wheels slip while the vehicle is turning, the split changes to 53:47. This info is taken directly from Toyota:
Toyota 4Runner Celebrates Historic Run with 40th Anniversary Special Edition - Toyota USA Newsroom
*note the section, “4x2 and Two kinds of 4x4.”
In execution, it’s sort of a mix between AWD and part-time 4WD. Power is still delivered to both axles via a center diff, but each axle has open diffs. You have all the benefits of a part-time 4WD system, full-time. The center diff allows for each axle to spin independent of one another and still offers the rear-power bias/adjustments. In a loss of traction, it adjusts dynamically. If there’s a loss of traction on both axles, youre still stuck, just like in a part-time 4wd system. If youre stationary, this is a much bigger problem than if you’re moving, where grip is changing constantly throughout your drive."