This board allows you to bring WiFi connectivity to your projects with the versatility that the ESP8266 module offers, with an Xbee compatible form factor it can be connected easily to any board with this connector like: Arduino Uno + XBee Shield, XBee IO Pro V2, PICARO+, among others
This product includes a modern ESP8266 processor running at 80MHz capable of various types of WiFi networking like client mode or Access point mode, it also supports the TCP/IP protocol stack and DNS.
IT HAS A 4Mb flash memory and has a built in PCB antenna. It comes with the NodeMCU firmware pre-loaded which will enable you to work with this board more easily but with the possibility of changing the firmware to work with AT commands or with the Arduino IDE.
Software and documentation: