A capacitor is a device that stores electrons and is made up of two conductors separated by an insulator. Capacitors come in various sizes, shapes, and can be customized. They are used to store electric charge and in circuits to block DC signals while passing AC signals. There are several types of capacitors including non-polarized, polarized, variable, and trimmer capacitors which differ in how they can be connected and whether their capacitance can be adjusted. Capacitors have many uses including in timing circuits, filters, and charge pump circuits.