As a junior training/studying in a martial arts school (or other schools), the purpose of training/studying as a beginner is to acquire knowledge. That knowledge is external as it is coming from a source (a teacher, books, videos etc) externally. You may or may not understand at first. Later on during your study or training that knowledge will manifest itself, meaning that knowledge will come from within, so internally. Just like my knowledge, that came from my teacher and the books that I've read like "Striking Thoughts" by Bruce Lee and "Reflection Volume 1" by Freddie Lee. Before I didn't understand what they were saying at first, then later I understand it by experience. So experiencing is what makes that knowledge manifest itself. It's like how Buddha teaches, which is something like "if you see what I see, then it is what it is"? (I can't really remember though). So he's not trying to force people to know what he is trying to say, all he's doing is sharing his wisdom or his knowledge, and all you have to do is take it, and the manifestation will come from within and you will start to realize and understand. So open up! just like in the "Celestine Prophecy" by James Redfield, you can read the book or watch the movie, but basically in the movie this woman was saying to this man to open up, meaning not to look with the mind, but with the soul. He did and he saw something beautiful, he saw that everything has energy radiating or vibrating at different frequency which he first saw that with plants. Then he started to see the world differently, the way that the woman sees it. So knowing comes from within when you see and experience what the source show, in this case the woman is the source that the man learned from.
An example for a physically activity is a technique that I learnt from my teacher (who is my friend and he was a senior student) in Kendo class. Well it wasn't a particular technique but it was how to execute a proper cut (any cuts- cutting techniques) by this one concept. At first I didn't understand it, but as I train hard I begin to realize and understand what he was showing me or teaching me. It took me like more then 100 cuts to feel it. So that knowledge came from within as I realized.
This applies to everything in life not just martial arts. Whenever something is acquired (knowledge) then that understanding will come from within as you experience it. And that my friends is knowledge within. Or maybe I should of said what comes within is wisdom, and what comes from the external is knowledge. As Bruce Lee would say "knowing others is knowledge, knowing yourself is wisdom."
My brain needs to rest, if I said something that is not right then that would be the reason, as well as my grammar errors but don't worry about it.