"K" is for knowledge of results and knowledge of performance.
Players need feedback as part of the development process. By themselves, they are constantly getting intrinsic feedback from their playing environment though visual, auditory and sensory means. But adults can positively provide feedback from an entirely different perspective.
It's important that player feedback comes in the form of knowledge of performance (how the player can improve) as opposed to knowledge of results. When a player makes a bad pass, he or she already has knowledge of the results. Feedback in the form of performance knowledge is what's needed from an instructor. And ideally, it should be presented in a format that is short, constructive and relevant to how the athlete can be better.