Do you know how a circuit works?
Do you know how to make a light bulb glow brighter or dimmer?
If the answer to these two questions is "no" then you need to brush up on the basics of electricity, especially if you are interested in putting together an electronic or electricity themed science fair project.
There are many ways that you can learn the basic concepts that relate to electricity, including reading text books and magazine articles. However, for most students, the best way to learn about the various components that are involved in the creation and utilization of electricity is to play around with these components in a controlled environment.
One tool that you can use to explore electricity and electronics is the MX-905 75-in-1 Electronic Lab.