Teaching others is teaching yourself

Taking in knowledge from a textbook, class, whatever the source may be, is one way of learning. But do you really know and understand the material? That question maybe answered if you can teach it too someone else. What you don't know you really can't teach. And trying to teach it but really can't is a good wake up call that you don't know the material. To teach someone you don't really require a degree, the first teachers, primarly parents, but I'm talking about people such as Aristole, and way before them, had no such thing as a degree but just knowledge. Through teaching other you also realize facts and understand concepts that you did not before.

So I am going to try my hypothesis on teaching and learning. Whatever it may be, economics, computer science class, from video games, I'm gonna try and teach it too someone else. And if they seem to understand just from my teaching, I think I would feel more confident knwoing wht I am talking about.

Is teaching the true way to learning?