More specifically, what are the pros/cons of each? Why do some cars use one system over the others and which is “better”?
EDIT: Thanks everyone for the explanations. It’s been very useful.
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These are indications of which wheels the engine actually turns. Front and rear wheel drive means that only 2 of the 4 wheels are connected to the engine.
Front wheel drive is usually more efficient in designs where the engine is at the front of the car, keeping all the drive components under the hood and no long shafts connecting the front engine to the back wheels. Brakes also like it because the heavier front end means when you brake and your weight is thrown forward, that’s good for the front wheels’ grip while braking.
Rear wheel drive is typically seen in performance cars where the fact that acceleration causes vehicle weight to shift backwards which helps the drive wheels grip better, but you also see it in trucks which have their heavy cargo or trailers at the rear for the same reason – grip while accelerating.
For AWD and 4WD, you need to understand that not all wheels spin at the same speed. When turning especially, each wheel does need the ability to turn at different speeds. In 2-wheel drive configurations, a device called a differential splits the power between the drive wheels while also allows that speed difference. With that said…
In AWD all wheels get engine power all the time. This is generally good for handling since no wheel(s) getting stuck should make it so you can’t move. However it requires 3 differentials – one to split the power between front and rear wheels, and then one for each set of wheels – or another very creative design. That’s a lot of gears to waste a bit of engine power, and a lot of parts to build the car, so these cars are usually most expensive.
4WD is a selectable mode, but it doesn’t provide that differential that splits power to the front and rear wheels and allowing their speeds to vary. You mostly see it on vehicles designed to off-road a bit, like pickup trucks, which are normally RWD. It’s meant for when you’re in a sticky situation, and spinning tires is expected. It will deliver power to the front wheels, but they must turn at the same rate as the rear wheels and the lack of that differential may force the tires to grind against the ground a bit. That’s fine for driving in the dirt, but not for real roads.
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