Nodejs integration for Chatroom I am following the Nodejs integration documentation to set up Chatroom, but am a little confused. 

In step 2, do we cd to the folder of nodejs installation, or the drupal nodejs module?

Also, what is the server.js file?
Updated the documentation page.

In step 2, we need to move in to nodejs module folder inside your drupal's sites directory. Install the dependencies using package manager(npm). Most probably the nodejs module is installed at sites/all/modules/nodejs.

Also don't get confused by these notation (path/to/your/nodejs/module/directory). It used to say that it exist in some directory.

server.js holds the code related to your express application from configuring your app to starting your app. Express will be installed in your node_modules folder when you install the dependencies. node_modules will be created in you nodejs module(drupal site).

node server.js starts the express application from the location where server.js file is present.

Also you can follow the tutorial links provided by No Sssweat.