A capacitor is used in circuits to:

A capacitor is designed to store electrical energy in an electric field between its plates when voltage is applied across them. This storage capability is crucial in various electrical and electronic applications, such as smoothing voltage fluctuations in power supply circuits, filtering out noise in audio systems, and timing applications in oscillators.

The mechanism behind this is that when a voltage is applied, charge accumulates on the plates of the capacitor, and this charge can later be released back into the circuit when needed. The ability to store energy is what distinguishes capacitors from other components in a circuit, making them essential for energy management and buffering in various electronic designs.