A circuit is a closed loop through which electrons will travel. Circuits need to have some type of electrical source, such as a battery, which will provide the necessary electrical energy to the circuit. The circuit provides a pathway through which the current will flow. The circuit will form a loop, so the start point and the end are the same. Circuits can be simple or complex, but all will share three of the same basic elements. They need a voltage source, such as the aforementioned battery. They also need to have the conductive pathway, or route through which the electrons pass. The circuit also needs a load, or the device that uses the electricity. A good example would be a light bulb.