A capacitor (originally known as a condenser) is a passive two-terminal electrical component used to store energy electrostatically in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric (insulator). Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. Types of Capacitor include Electrolysis Capacitor, Ceramic Capacitor, Multiple layer Capacitor, Chip Capacitor, Mylar Capacitor, Polypropylene film, Safe Y-Capacitor.