Capacitor is a two terminal passive electrical component. It is used to store energy in an electrical field. Capacitor works as a voltage source. The capacitor is used widely and its forms contains at least two electrical conductor separated by a dielectric material, one common construction consists of metal foils separated by a thin layer of insulating film. In electrical circuit capacitors are widely used as a parts.
The static electric field develops across the Di-electric when the voltage or potential difference is applied across the terminals. This occurs when negative charge is on one plate and positive charge on the other plate. Mainly electrical energy is stored in the electrostatic field. An ideal capacitor is characterized by a single constant value capacitance and measured in farads. So we need to know the measurements of capacitor value using the figure. For more information go wikipedia.