In electrical circuits, resistors oppose the flow of charges around a circuit. They are usually made of wire or a ceramic material. Some typical resistors are shown below. In the simplest circuit consisting of a single battery and a single resistor, there is a relation between the voltage, V, the current, I, and the resistance, R, which is known as Ohm's Law. They are like a spring which when compressed or stretched stores mechanical energy.
Capacitors store electrical energy.
Capacitors consist of two metal plates with an insulting material between them. The two metal plates are charged one positively and the other negatively, although the charges do not pass between them. The unit of capacitance, C, is the Farad . A farad is a very large unit. In some capacitors the insulating material between the plates is air as in variable air capacitors.