Quite true. Best way to learn is to teach. I learn more when I
  try to explain than I do when studying. I live by this. As soon
  as I think I understand something, I try to explain it quickly
  to somebody else. Doesn't matter where. I judge by the responses
  whether I think they 'get it' but really, to be selfish, it's
  not whether they get it or not. It's whether I'm satisfied with
  how I explained it - the feedback though helps me find out if my
  self-assessment needs tweaking or overhauling.