Working with SASS
Slate was designed to encourage a modular workflow. The days of 10,000 line stylesheets are best left in the past.
Slate is setup to work in a modular fashion.
site.scss is meant to be used to import other stylesheets, although you can of course write all your styles in this file if you want to.
_site-config.scss contains Slates configuration variables that control how it behaves. These are explained in detail in this guide.