It is an Open-source, Interactive, Programmable, Low cost, Simple, Smart, WI-FI enabled board which can help you to build IOT projects with ultra fast prototyping.
The Development Kit based on ESP8266, integrates GPIO, PWM, IIC, 1-Wire and ADC all in one board. Power your development in the fastest way with NodeMCU Firmware! .
Cost: Around 8$ you can have this powerful board at your command:)
The Only thing that will disappoint is you that , it works on 3V logic and you have to make arrangements when connecting sensors which work on 5V
This board has 30 Pins and refer the Pin diagram for better understanding.
About the hardware
The ESP8266 is a great chip with built-in WiFi. It was originally used with Arduino boards to WiFi-enable hardware projects but soon became a cheap standalone Arduino-compatible development board. It comes in many shapes and forms and is most famous in development boards such as NodeMcu, Adafruit HUZZAH, or the SparkFun ESP8266 Thing.