MOD-WIFI-ESP8266 is an add-on module featuring the ESP8266 WiFi SoC with a W25Q16B SPI Flash memory IC. It can connect to a host system via its UEXT connector. The board has a PCB trace antenna.
Solder jumpers allow you to do some I/O configuration (refer to the schematic for details).
Note: Because this module is designed for inclusion in a larger device, it does not have FCC or CE certification of its own.