How does your car go around corners without screeching tyres? That's the magic of the differential, a seemingly complex meshing of various gears and splines that delivers separate power to each driven wheel. This pre-World War II video produced by General Motors is actually an incredibly straightforward and informative look at what goes on underneath your car to make it move.
This video, narrated by one of the smoothest voices you'll ever hear, quickly and simply demonstrates how a differential works. Instead of a single, live axle driving both wheels at identical speeds, a meshed differential lets each wheel move independently according to the friction it experiences from the road surface, all the while delivering constant power from the engine attached to the drive shaft.
Now, for your homework, try and work out how a limited slip diff works, and explain it as best you can in the comments below.
Bonus: This one's a little more out of date, but this 1937 video from GM will give you a basic education on how a carburetor works: