NodeMCU is an open-source firmware and development kit that helps you to prototype or build IoT products. It includes firmware that runs on the ESP8266 Wi-Fi SoC from Espressif Systems, and hardware which is based on the ESP-12 module. The firmware uses the Lua scripting language.
There are two common variations of NodeMCU: v0.9 and v1.0.As obvious version 1.0 is the latest and loaded with more features
For detailed technical data visit official page here