"What’s the key to effective learning? One intriguing body of research suggests a rather riddle-like answer: It’s not just what you know. It’s what you know about what you know.
To put it in more straightforward terms, anytime a student learns, he or she has to bring in two kinds of prior knowledge: knowledge about the subject at hand (say, mathematics or history) and knowledge about how learning works. Parents and educators are pretty good at imparting the first kind of knowledge. We’re comfortable talking about concrete information: names, dates, numbers, facts. But the guidance we offer on the act of learning itself—the “metacognitive” aspects of learning—is more hit-or-miss, and it shows."
Via Beth Dichter