ESP8266 ESP-12E Wi-Fi Specs:
802.11 b / g / n wireless standards;
STA / AP modes support ;
TCP / IP protocol stack, One socket;
Supports standard TCP / UDP Server and Client;
Supports serial port baud rate configuration: 1200/2400/4800/9600/19200/38400/57600/74800/115200 bps;
Supports serial data bits: 5/6/7/8 bits;
Supports serial parity: none;
Supports serial stop bits: 1/2 bit;
Pin-compatible with Arduino UNO, Mega;
Arduino Pinout 2/3/4/5/6/7/8/9/10/11/12/13;
ESP8266 GPIO Pinout 0/2/4/5/9/10/12/13/14/15/16 / ADC / EN / * UART TX / UART RX;
KEY button: modes configuration;
Dual-Ports DIP switches: switching Arduino and ESP8266;
WiFi operation current: continuous transmission operation: ≈70mA (200mA MAX), idle mode: <200uA;
Serial WiFi transmission rate: 110-460800bps;
Temperature: -40℃ ~ + 125 ℃;
Humidity: 10%-90% non-condensing;
Weight: about 20g (0.7oz);

The Shield has two LEDs. Red LED is donated to the power supply. Blue LED is a multi-functional LED and its functions are:

Blink 4 times continuously	Data communication
Blink 1 time every 0.5 s	Configuration modes
Blink 1 time every 1s	Connecting router in STA mode
Steady-on	AP/STA working mode