When you start working with WebPack for GameTime, you'll notice that you can't just define a variable in one file and find it in another as easily as you can in Rails.
Read Node.js, Require and Exports and Organize Your Code with RequireJS
Modules are specific parts of code that live in their own files. This allows better orginization of code. In order to use these code modules they need to be exported and specifically required them from other files. This makes code easier to read and handle.
The second blog post uses require.js to create modules split out in different files. This approach uses different syntax to create modules (define() instead of defining vars and functions). Exporting specific code is not necessary with require.js but it also uses require() in order to use functions from other files.