This is the Sonoff Basic R3 DIY smart switch. For more detail about the product you can visit the manufacturer's website: https://www.itead.cc/sonoff-basicr3-wifi-diy-smart-switch.html

The switch supports two modes: The default eWeLink mode which allows control through the eWeLink app as well as various home assistants. The DIY mode, which allows you to control the device through a REST API. The Sonoff DIY Android app allows you to control the device in DIY mode.