The Feynam Technique is a Mental Model named after Richard Feynman, a Nobel Prize Winning Physicist. It is designed as a technique to help you learn pretty much learn anything - so understand concepts you don't really get, remember stuff you have already learnt, or study more efficiently.
The Feynman Technique was actually a big inspiration for this blog - I try and apply this to a lot of the concepts and Mental Models that I write about.
The technique can be broken down into four easy steps, but first a quick video from Scott Young that sums it up very simply.