An ON/off switch, also known as a toggle switch, is a type of switch that can be used to control the flow of electricity in a circuit. It is typically composed of two positions, 'ON' and 'OFF', which are connected by a lever or handle. When the switch is in the 'ON' position, electricity flows through the circuit, and when it is in the 'OFF' position, the circuit is broken and no electricity flows. The term 'toggle switch' comes from the fact that the lever or handle moves back and forth, or 'toggles', between the two positions.