This is ESP-12E: ESP8266 Serial Port WIFI Wireless Transceiver Module For Arduino.
 
This small WIFI transceiver is the perfect solution for home Automation and IoT applications. It can be the replacement of your NRF24L01, it can talk to your WIFI router directly through the UART MCU’s (Rx, Tx).
 
The ESP-12 module is one of the most complete of the ESP family as it allows you to use the biggest amount of pins of all of them. You can program this module to work stand alone with the Arduino IDE or with LUA as NodeMCU.
 
The system is equipped with ESP8266 manifested leading features are: energy saving VoIP quickly switch between the sleep/wake patterns, with low-power operation adaptive radio bias, front-end signal processing functions.
 
The ESP8266-03 is one of the smallest versions of this module. It includes a built-in ceramic antenna.