A capacitor is a fundamental electronic component designed to store electrical energy in an electric field. It typically consists of two conductive plates separated by a non-conductive material called a dielectric. The capacitance, measured in farads, quantifies the component's ability to store charge and is influenced by the geometry of the plates and the dielectric constant of the intervening material. Functionally, capacitors can act as temporary energy reservoirs in DC circuits, smoothing voltage fluctuations and maintaining signal integrity, while in AC circuits, they are used to introduce a reactance that can be tuned for specific filtering or coupling applications.