Video: The joule can be a confusing enough form of measurement for adults, but the folks over at Adafruit managed to distil how joules work for a younger audience. As these things go, the video's just as useful for confused adults. A joule is equal to the amount of energy transferred or the work done. In basic terms, it's a unit of measurement that measures how much effort it takes to do something. For example, it takes approximately one joule to lift an apple about a metre up from the ground. It gets a little more confusing when you apply that same measurement to something like lightbulbs, but the above video explains it in a simple enough way that anyone can understand.
Circuit Playground - J is for Joule [YouTube]