If you don't know what CSS and don't care, this post is not for you. Watch this video and move along. 🙂
For those of you who do care about CSS, SASS is a new-ish preprocessor. So basically you write stuff in SASS and it turns into CSS.
For example in CSS you have to explicitly define every color. If you want a certain shade of a color you have to type in #e5f4g6 (not a valid color code of course) In SASS, at the very beginning of your code you define that color ( #e5f4g6) as "blue2". So every time you want that shade of blue you just type blue2. Much simpler and easier to remember.
If you want to know more, read this article on CSS preprocessor. That is all.