A switch is an electrical device that can open or close a circuit, allowing or stopping the flow of electricity. It typically has two positions: on and off. When the switch is in the "on" position, it completes the circuit, enabling electrical devices like lights or fans to operate. In contrast, when it is "off," the circuit is broken, and the devices do not receive power. Switches come in various types, including toggle switches, push-button switches, and rocker switches. They are commonly used in homes and industries to control lighting, machinery, and other electrical systems, making them essential for everyday operations.