In a way, a capacitor is a little like a battery. Although they work in completely different ways, capacitors and batteries both store electrical energy. If you have read How Batteries Work, then you know that a battery has two terminals. Inside the battery, chemical reactions produce electrons on one terminal and absorb electrons at the other terminal.
Flash capacitor from a point-and-shoot camera
A capacitor is a much simpler device, and it cannot produce new electrons -- it only stores them. In this edition of HowStuffWorks, you'll learn exactly what a capacitor is and how it's used in electronics.