Relays are electrically operated switches that use an electromagnet to control the flow of electricity in a circuit. They consist of a coil, one or more sets of contacts, and a mechanical linking mechanism. When an electrical signal is applied to the coil, it generates a magnetic field that moves the linking mechanism and opens or closes the contacts, allowing current to flow through the circuit. Relays are commonly used in industrial automation, control systems, and electronic devices to remotely control power, switch circuits, and protect against overloads and faults. They offer high reliability, long lifespan, and low power consumption, making them essential components in many industries.