As the line between designer and developer continues to blur, we need more from CSS than it can offer. Sass is an extension of CSS that adds basic features CSS is sorely missing (like variables and nesting). But Sass kicks things to a new level with mixins (flexible, re-usable blocks of CSS) and advanced selector inheritance. Simply put, Sass makes CSS authoring fun again.
Clipping is a handy way to collect important slides you want to go back to later.