1. Capacitors that consist of tiny storage batteries which charge and discharge rapidly.

Made of two plates separated by a thin insulator or sometimes air, when one plate is charged negative and the other positive, a charge builds up and remains after the current is removed.

When electric power is required, the circuit is switched to conduct current between the plates, and the electrical charge is released.

2. An electronic component that stores an electric charge and releases it when required.

It comes in a huge variety of sizes and types for use in regulating power as well as for conditioning, smoothing, and isolating signals.

Capacitors are made from many different materials, and just about every electrical and electronic system uses them.