It's amazing how much knowledge has been lost throughout human history. Most of what we know now are just being rediscovered, even this method of learning can be found in ancient Greek philosophy; Lucius Seneca (a Roman philosopher) said in one of his epistles, "we are learning if we teach."
The traditional way of learning is to listen and try to assimilate what the teacher or mentor is trying to pass on to the learner. That is traditional education as we know it, students today are basically data recorders, recording from various sources; oral, digital media or written.
source
Teaching others to learn faster isn't just a new thing. In fact, in the 1980's, Jean-Pol Martin a German professor also re-established this method of learning by introducing it to his student through peer-2-peer learning. Students would choose parts of a Topic to explain to each other in a non-traditional and interactive mode of teaching.
He had huge success with that method and was able to spread this practise of teaching to so many Teachers in the country.
Scientists have also discovered that the reason why this method is very effective is due to the protégé effect. By having the mindset to teach others a particular topic, your mind becomes aware of the learning process and you are not just learning for learning sake. You begin to gain a new perspective and understanding on that particular topic
Very often I think I finally grasp something until I am forced to teach someone else, then I begin to notice the holes in my understanding. I remember once, I was trying to teach something to a friend by solving a math-problem, as I began to solve I noticed I gained a new understanding of the subject. It was a learning experience for the both of us.
Apart from being a student in a classroom, we are also students of life, we acquire life skills from different means. teaching others can be very instrumental to your learning curve.
If you think you fully understand a topic, I want you to take your time to break it down to someone. You will be surprised to notice that it will be a learning experience for the both of you.