This is D1 Mini V2 NodeMcu 4M Bytes Lua WIFI Internet Of Things Development Board Based ESP8266, it is a mini WIFI board based on ESP-8266EX. 11 digital input/output pins, all pins have interrupt/PWM/I2C/one-wire supported(except D0) 1 analog input(3.3V max input) and a Micro USB connection.

The development board features WiFi-SoC ESP8266 and is made for fast Internet-of-Things (IoT) prototyping. It is flashed with the latest firmware version and can be set up and programmed right away with the onboard micro USB connection. With only a few lines of code, the NodeMCU Dev Kit connects to your local network and ready for control by other network members like computers and smartphones.

The d1 mini is an ESP8266 development board that is compact, versatile and very easy to use with the Arduino IDE. It supports natively by the Expressive SDK.

Features :

1. Use BRT (Bias Resistor Transistor)
2. Easier into flash mode.
3.  30% increase in radiating area
4. Good stability.