what is node.js

                                    Node js allows you to run javascript outside of your browser
ex: you are able to run it on your terminal

                                    NodeJs is Runtime environment for executing Js code, Outside Of Browser.
it is build upon Chrome v8 engine using c++.

Uses of Node:

-can build back-end services like API which can be used as backend for 
diferent platform Apps(Website, MobileApp, Desktop App).

-is Asynchronous by default means Single thread handle all the request
and response, thereby providing more speed, highly scalable, built time half 
compare to other tech in market, 33% few line of code, 40% fewer files,
can handle 2times more requests/secs, 35% fast response time.
// Hope you like the short Description.

                                    npm install http then write a webserver...
const http = require('http');
const PORT = 3000;

const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end('Hello World');
});

server.listen(port, () => {
  console.log(`Server running at PORT:${port}/`);
});

                                    Express is a minimal and flexible Node.js web application framework
that provides a robust set of features for web and mobile
applications.

                                    When you install Node.js, you can do these things:
Make web servers
Run JavaScript without an HTML file
...and more!