Feynman Technique is a learning-by-teaching technique where you try to explain an idea, which you are studying, as to a 12-year-old child. If the explanation is not simple enough or too confusing, this means that you don’t really understand the topic, and you need to either to review the topic or refine your rhetoric.
That being said, it is not scientifically tested, and its theory is contradictory. Since different people have different cognitive ability, some information will lose due to the simplification in order for the listener to understand. This means that although the explanation could satisfy for a 12-year-old child, it doesn’t necessarily mean that the explanation is clear and verbose to more advance leaner.
See Dialogic Learning for scientific approach to learning or teaching that is similar to this.