The ways of communication between switch and the fixture without wiring

1.   wireless transmission: A wireless receiver / lighting controller is typically wired or screwed into a fixture or device, wired or otherwise connected to the electrical system of the building or plugged into an outlet. The wireless receiver's memory is programmed by any number of means to respond to certain selected "switches" or (more correctly) remote control transmitters.

2.    the existing power lines: A receiver is plugged into an outlet and a device is then plugged into the receiver. The plug-in receiver is then programmed to the switches. Some devices are hard wired into ceiling light fittings, making for a hidden system.