What is Node.js and how to install it ?

Node.js

• A JS runtime
• Server side
• Open source
• Asynchronous
• Event driven framework
• Single threaded
• Lightweight - due to non-blocking I/O model

• Designed without threads
• No locks = No deadlocks
• Process never blocks on I/O
• Produce data in chunks

• Code is written in JS and Node.js interpreter runs the code

Download it from : https://nodejs.org/download/ 
Extract the tar.gz file and copy the extracted directory to /usr/local/nodejs
In windows, install with MSI file and add location C:\program files\nodejs\bin to PATH env variable.