If you’d like to do some home automation work, the ESP8266 module is a great place to start. Featuring built-in WiFi, you can use it to control something via a smartphone app or whatever other method you desire.
By itself, however, use can be a little complicated. It certainly can’t be directly powered by or switch household voltages, so you’ll need to wire up a relay and power supply. Or at least you did.
With this board by Bmo Technology, all of that is already provided for you. It features an ESP8266 module that is set up to work with 100-240 VAC via its normally open relay and a 3.3V power supply.
This module’s creat0r was reportedly tired of going outside to turn off his exterior Christmas lights, so he created this to control them through his phone or via a timer. Of course working with mains voltage means you need to know what you’re doing. But placing the module on the board and taking care of the power regulation at the same time alleviates the challenge of building all of these as discrete modules into one junction box.