This ESP8266 WiFi Shield is designed specifically to connect your Arduino to the internet wirelessly through ESP8266. When working with esp8266, it is not necessary to mount a circuit with several components and wires to interconnect an ESP8266 to the Arduino. By simply connecting the board to the Arduino, position the DIP switch path according to the shield operating mode, and program the Arduino to connect to WiFi networks. Moreover, the board can be operated without the Arduino, as it has all the pin-outs of the ESP-12E available.
This shield allows an Arduino board to connect to the internet using the Wi-Fi library. And to read and write to an SD card using the SD library. This ESP8266 shield is mounted on the top of an Arduino board (e.g. the Uno). And connects it to your computer with a USB cable as normally to upload the sketches to the board. Once the sketch has been uploaded, disconnect the board from your computer and power it with an external power supply. The WiFi Shield supports wireless networks that operate according to the 802.11b and 802.11g. The Digital pin 7 functions as a handshake pin between the WiFi shield and the Arduino, and should not be used.
The ESP8266 Wifi module was designed based on an integrated chip specifically to fulfil the needs of a new connected world. It can handle all the necessary overhead for communicating with your network, such as TCP/IP stack and communicating with your 802.11 networks. ESP8266 was designed as a Serial Wifi Wireless Transceiver Module with self-contained SOC and integrated TCP/IP protocol stack. It gives access to any microcontroller to your WiFi network. This wireless module is completely addressable over SPI and UART protocols.