A capacitor stores electrical energy in an electric field created between two conductive plates separated by an insulator. When voltage is applied, the capacitor charges, leading to a current flow until it reaches its maximum charge capacity. The I-V graph of a capacitor shows a nonlinear relationship, with current decreasing as the voltage across the capacitor increases. Capacitors are essential in various electronic applications, including filtering and energy storage. Understanding their operation is crucial for effective circuit design.