The MinutePhysics video series does an amazing job of breaking down complex ideas and adding some awesome cartooning work to be learning fun. In their latest video, they cover the concept of angular momentum.
As the video says, angular momentum describes the "oomph" of things traveling in circles, just like regular momentum describes the "oomph" of things traveling in a straight line.
By understanding the way that rotating things move, we can understand the motion of things as small as electrons in an atom, to much larger things such as our solar system around in galaxy.
Check it out!