An industrial relay is essentially an electromechanical switch that uses an electromagnetic coil to control one or multiple contacts. When electrical current flows through the coil, it creates a magnetic field that moves a mechanical armature. This action either opens or closes the contacts, enabling or disabling the flow of current in the connected circuit. Relays can handle various voltage and current levels, allowing them to control high-power devices from a low-power control signal. This makes them invaluable in automation systems that require reliable switching and isolation.