This is a switch ,unlike conventional switch has a relay and a wireless chip inside , this will sit behind your switch box ,you can blank you existing fan/light switch and put this inside the switch board - warning be careful if you are not familiar with power use an electrician.-the input comes on one side the output through the other clearly marked.It is now 100% controllable by Alexa and also Sonoff has an App running on your phone through which also you can control.There is a video by Sam9 i think somewhere in this forum under home automation.