Base contains global settings, variables, resets, and mixins. These make up the foundation of your CSS.

Elements contains all the global styling for basic stand-alone elements; such as links, quotes, tables, and text.

Layout contains structural helper classes like .container , which restricts content to a consistent max-width, and a responsive grid system as well.

Modules are custom-made components that are used throughout your site. These include global modules like the site header and footer, and other reusable modules like alerts and heroes.