Here's what I found from:
http://auto.consumerguide.com/auto/e...?act=feature06
All-Wheel-Drive Versus Four-Wheel Drive
Not All Systems are Created Equal
With one exception--the Lincoln Blackwood--all sport-utility vehicles (SUVs) and pickup trucks are available with 4-wheel drive. There are even several cars and minivans that offer all-wheel-drive systems. But there are substantial differences in the types of 4WD systems offered. The most important determining factor is whether 4WD can be left engaged on dry pavement. Some 4WD systems must be "turned off" on dry pavement to avoid mechanical damage. Others can be left engaged, a convenience that relieves the driver of deciding when 4WD is needed. Here is a more detailed description of each system. In some cases, more than one system is available for a given vehicle. We describe 4WD systems based on the above criteria. What follows is a further explanation of how each functions:
Type 1: 4WD that must be disengaged on dry pavement.
Also known as part-time 4WD, this is the most basic system. The transfer case provides a choice of settings, usually 2WD, 4WD High, and 4WD Low. In current model year vehicles, it can be shifted from 2WD to 4WD High "on the fly," which means while driving down the road, but 4WD must be disengaged when running on dry pavement. This is because the transfer case provides a 50-50 power split, and there's no mechanical compensation for the differences in tire speeds that occur when rounding corners. Leaving 4WD engaged on dry pavement causes the transfer case to wear--and eventually fail. Repairing a 4WD transfer case is expensive. These systems are inconvenient in conditions of light rain or patchy snow because they must be switched back and forth while driving. To engage 4WD Low, which is typically used only in severe off-road driving, the vehicle must be brought to a complete stop.
Type 2: 4WD that can be left engaged on dry pavement.
Also known as full-time 4WD, this system is more advanced--and more convenient. The transfer case has a choice of settings, usually 2WD, 4WD High, and 4WD Low, sometimes adding an Automatic 4WD or Full-time 4WD setting. These systems can be left engaged even when running on dry pavement. To engage 4WD Low, which is typically used only in severe off-road driving, the vehicle must be brought to a complete stop.
Type 3: All-wheel-drive.
This system locks both axles and distributes power in varying degrees to all four wheels automatically when it detects wheel slippage. The transfer case is always in 4WD, so the driver doesn't have to bother with a switch. Take a look at the table that follows to find the few vehicles that offer low-range gearing--useful only in severe off-road driving--with their AWD systems.
False Sense of Security
Keep in mind that while 4WD helps you "go in the snow," it does little to aid cornering ability and virtually nothing for braking. Many drivers, finding they can accelerate in snow as quickly as on dry roads, assume they can corner and brake as well. This is untrue, and often leads to over-confidence, which in turn leads to accidents.
Which System Is Best for You?
First, note what kind of driving you generally do. Are you searching for a heavy-duty work truck, or a daily driver to get you to and from the office? Do weather and road conditions often hinder your driving, or do you spend most of your "drive time" on well-maintained streets? Once you know what you need from a vehicle, you can start to determine the one that best suits you. We've compiled a listing of all 2002 model year vehicles that offer 4WD or AWD systems, to help you see the options more clearly. You'll note that Dodge Dakota is the only compact pickup truck to offer Full-time 4WD, but there are several full-size pickups that come so-equipped--Chevrolet Avalanche, Silverado 1500/2500, and Sierra 1500/2500. Select SUVs like Land Rover's Discovery and Range Rover, Mercedes-Benz's M-Class and G-Class, as well as the Jeep Grand Cherokee, Lexus LX 470, and Toyota Land Cruiser offer low-range gearing along with AWD for serious off-road work. If you're not looking for a truck or SUV, but still want the convenience of all-wheel drive, check out Subaru and Audi models (Impreza, Legacy/Outback, A4, A6/allroad quattro, or A8). The following table indicates which vehicles may offer the system you're looking for. As you scroll down, click on the vehicles that interest you to read our reviews or get ratings and prices.
4wd and Awd
of course if you find a car with 6 wheels like the Corvini maybe and all of them are driven by the engine, well, if you say AWD it actually is 6WD 
Hybrid Mode
