NPM

NPM is a package or module manager for Node.js packages or modules. NPM gets installed along with Node.js.

When you install a package it gets stored in node_modules folder.

How to download a package

npm install <package-name>

How to use the package in your code

let app= require('express');
// express is the package name

Note

You can find thousands of packages for free @ NPMJS with verbose documentation.