Many envisage electricity as the "power" to "do things." They know that electricity needs "circuits" and that something is "flowing" in the circuits, but they are not sure what or why. Words such as "current" and "voltage" are part of electricity but their meaning, and the difference between them, is not always clear. In this article, the authors have tried to present the basic ideas teachers need to know in order to understand what is happening in simple circuits. They also describe some models and analogies that have helped children and teachers get a "feel" for what is happening in the circuits they have set up. (Contains 8 figures.)