A little bit of engineering...

Few days ago, i stumbled across a nice little video about differentials, in cars. Only then i realized that i didn't know much about them. And this video really explained a lot. You might have known that first cars had only one-wheel drive, which means the car's engine was only powering one wheel. Still, there was a problem which was obvious when the car was turning. The wheel that wasn't powered was actually "slowing" the car. After a while a two-wheel drive was invented. It was much better at turning than the previous one, but still had a problem. The thing is, when you're powering two different wheels with one engine, you are actually making them turn together at all times. So, both wheels are rotating at the same speed, always. That is a problem when turning. If you're turning left, for instance, the left wheel travels a shorter way and thus rotating slower, and the right wheel has to rotate faster and travel a bit more than the left one so it can keep up. Because both wheels are locked together, this causes sliding, which can break the wheel or slow down the car. So, a device needed to be invented to allow both wheels to rotate freely. This device was invented and is now called the differential.

What it does is, it allows the engine to power both wheels while letting them turn like both of them were powered separately. This greatly reduced sliding, and prevented possible damages to the engine and wheels.

If you would like to know how it works, here's a video that i watched