Feather HUZZAH - ESP8266 WiFi with Stacking Headers
This is the Adafruit Feather HUZZAH ESP8266 - an 'all-in-one' ESP8266 WiFi development board with built in USB and battery charging. At the Feather HUZZAH's heart is an ESP8266 WiFi microcontroller clocked at 80 MHz and at 3.3V logic. The SiLabs CP2104 USB-Serial chip can upload code at a blistering 921600 baud. The USB interface lets you quickly use it with the Arduino IDE or NodeMCU Lua. (It comes preprogrammed with the Lua interpreter).
More information is available on the website of Adafruit.