The document discusses the importance of knowing what students already know (K), what the teacher wants them to learn (W), and what they should have learned by the end of a unit (L). It provides an example applying this K-W-L framework to a unit on electricity. Specifically, it notes that before the unit students knew electricity powers appliances but had to pay for it, the teacher wants them to learn about electrons, electric circuits, and energy sources and production, and by the end students should have learned about electrons, renewable and non-renewable energy sources, and the costs of electricity.