A capacitor is a device that stores electric charge in an electric field. It is a passive electronic component with two terminals. High capacitance capabilities (1000s of µF) allow these capacitors to store a great amount of energy for their size. There are a few different types of electrolytics, but they mostly use a very thin layer of oxide as the dielectric and a conducting semi-liquid electrolyte as one of the plate electrodes. These polarized capacitors are often used in coupling, ripple smoothing, DC blocking, bypassing, filtering and timing applications.
Box: Capacitor 2