We are often presented with an idea of learning that goes something like this... We're presented with some information or a concept. We study that information until we think we've got a proper grasp on it. We're tested on that information, either by an educational institution or by practical application, and we determine a degree of mastery from that test. If we are determined to have mastered the material, we can then graduate to the next level of learning. That's how 4th graders become 5th graders, so to speak.
This depiction of what it means to learn is based on a bit of a flawed premise, and that premise is the idea that learning is linear. If you start at point A (not knowing the information) and you continue to point B (knowing the information), your journey from those two points appears to be linear. And, in isolation, that's kinda true. But when we take that concept into our walking, talking, doing, feeling, physical lives, we are left with some questions. "I thought if I did this, I would get this result. What happened?" "I thought I was past this issue. Why is it here again?" "I already know this. Why am I having to learn this again?" Go with me on this for a sec. Imagine standing at the base of a very tall mountain, so tall that the peak is shrouded in the clouds. And right in front of you is a path that winds circularly around the face of the mountain. You can also see path that leads straight up the side of the mountain. (If you've seen Ace Ventura 2: When Nature Calls... ya know that staircase that he sends the slinky down?... like that.) You think, "Well, the path straight up the side of the mountain is faster. I'll get the information quicker, and I'll be certified an expert." But then you pause for a moment, realizing that you've been disappointed by that frame of mind before. See the questions that we've laid out above. (That, right there, is DEEP LEARNING, in and of itself. Realizing that something didn't work, and taking steps to change the course.) So, you decide instead to take the path that circles the mountain. (Continued in the comments...)