A capacitor is a passive two-terminal electronic element that stores electrical energy in an electric field. The result of a capacitor's performance is known as capacitance. A capacitor is a part designed to add capacitance to a circuit.
Capacitors are used in electronic circuits for blocking direct current while allowing alternating current to pass. Capacitors are used in electronic circuits for preventing uninterrupted flow while still allowing alternating current to pass.
In analog filter networks, they level the output of power supplies. In resonant circuits, they tune radios to distinct frequencies. In electric power transmission systems, they balance voltage and power flow. The property of energy storage in capacitors has been exploited as memory.