Bourbon - Bringing it All Together

In this last video, we bring together everything from Sass, Bourbon, Neat, Bitters and Refills to style a Rails application. Tyson shows us his real process, and explains the thinking and choices at each step.
This is a companion discussion topic for the original entry at https://thoughtbot.com/upcase/videos/bourbon-bringing-it-all-together

What is the difference between base, patterns and components folders? It wasn’t clear to me.