The ESP8266 WiFi Module is a self contained SOC with integrated TCP/IP protocol stack that can give any microcontroller access to your WiFi network. The ESP8266 is capable of either hosting an application or offloading all Wi-Fi networking functions from another application processor. This module comes with AT commands firmware which allows you to get functionality like arduino wifi shield, however you can load different firmwares to make your own applicaiton on the modules' memory and processor. Its a very economic module and has a huge and growing community support.
This module has onboard 80Mhz low power 32 bit processor which can be used for custom firmwares. This also means that you can host small webpages without any external controller. For more details see : NODEMCU . The ESP8266 supports APSD for VoIP applications and Bluetooth co-existance interfaces, it contains a self-calibrated RF allowing it to work under all operating conditions, and requires no external RF parts.
ESP8266 is transforming the world with its low cost and high features which makes it an ideal module for Internet Of Things (IOT). It can be used in any application where you need to connect a device to your local network or internet.This module ESP-12 has 7 GPIOs.
Note: The ESP8266 Module is compatible only with 3.3V logic level and will not work directly with 5V devices (for both serial and GPIO access). You need a 3.3V compatible device or you will need to convert the levels before you use it.