npm

npm , short for Node Package Manager, is two things: first and foremost, it is an online repository for the publishing of open-source Node.js projects; second, it is a command-line utility for interacting with said repository that aids in package installation, version management, and dependency management.

JavaScript is quickly becoming the go-to language for web developers. Front-end web developers use JavaScript to add user interface enhancements, add interactivity, and talk to back-end web services using AJAX. Web developers who work on the server-side are also flocking to JavaScript because of the efficiencies and speed offered by JavaScript’s event-driven, non-blocking nature.

In fact, concentrating on JavaScript as your language of choice offers the opportunity to master a single language while still being able to develop “full-stack” web applications (FE and BE). The key to this server-side JavaScript revolution is Node.js® — a version of Chrome’s V8 JavaScript runtime engine — which makes it possible to run JavaScript on the server-side.

Node.js is also used for developing desktop applications and for deploying tools that make developing web sites simpler. For example, by installing Node.js® on your desktop machine, you can quickly convert CoffeeScript to JavaScript, SASS to CSS, and shrink the size of your HTML, JavaScript and graphic files. Using NPM — a tool that makes installing and managing Node modules — it’s quite easy to add many useful tools to your web development toolkit.

Node isn’t a program that you simply launch like Word or Photoshop: you won’t find it pinned to the taskbar or in your list of Apps. To use Node you must type command-line instructions, so you need to be comfortable with (or at least know how to start) a command-line tool like the Windows Command Prompt, PowerShell, Cygwin, or the Git shell (which is installed along with Github for Windows).

http://blog.teamtreehouse.com/install-node-js-npm-windows

Anywhere in command prompt test node: node -v