Node.js is an open source and cross-platform runtime environment for executing JavaScript code outside of a browser. NodeJS is not a framework and it’s not a programming language.Developers prefer to use Node.js because it is easily scale the application in both horizontal and vertical direction. We can also add extra resources during the scalability of application. It is an open source, a server-side script which runs on the top of Google’s open-source scripting engine V8. Node.js is fast, lightweight and efficient. It uses the asynchronous mode of operation, event-driven Input/Output rather than using the traditional threads or separate threads for each process.