Mario and Fafa from Glove and Boots explain Joseph Campbell's famous theory in a very clear and visual manner. If you're not into muppets and puppets, just close your eyes for a second when these two guys explain the Hero's Journey theory: all great stories include the same characters. If you don't know it - just watch it, it 'll all make sense.
And if you've got some time to spend - browse through the Glove and Boots channel on YouTube. The guys behind this are hugely talented (in more often than not: hilarious) storytellers.