Metacognition is "thinking about thinking" — monitoring and regulating your own learning as it happens.

It has two parts: monitoring (noticing what you do and don't know) and regulation (changing what you do next — more practice here, move on there). Almost every study decision you make is downstream of a metacognitive judgment: what to review, what to skip, when to stop.

That's why accurate self-assessment matters more than it sounds. If your sense of "I've got this" is wrong, you'll pour time into the wrong material and abandon exactly the things you haven't actually learned. Good technique is wasted if it's aimed by a broken gauge.

A judgment of learning (JOL) is your prediction that you'll be able to recall something later; calibration is how well those predictions match your actual performance.

A well-calibrated learner's confidence tracks reality: high confidence on things they truly know, low confidence on things they don't. A poorly calibrated learner is confidently wrong — sure they'll recall material they'll actually blank on.

Calibration is the practical payoff of metacognition. Poor calibration causes bad study decisions: you stop studying things that feel known but aren't, and you'll only discover the gap at test time, when it's too late to fix.