A capacitor is an electrical component used to store electrical charge, block DC current, or filter low frequencies out of a signal.
A capacitor consists of two large-area plates of conductive material separated by a thin insulator. To make the structure compact, the plates are made from thin flexible sheets, which can be rolled up. Each sheet is then connected to one of the capacitor's leads.
If a current, carried by electrons, is pushed through a capacitor, excess electrons accumulate on one plate. The excess charge repels electrons from the opposite plate, and they leave out the other lead. The longer the current flows, the more charge accumulates and the more voltage is generated across the capacitor. If the capacitor is then removed from the source of current, the voltage may persist indefinitely.