This document compares LESS and SASS, which are meta-languages that extend CSS to allow variables, mixins, and other features. LESS processes stylesheets with JavaScript, while SASS uses the Ruby programming language. Both aim to make CSS more modular and reusable. The document discusses how each works, their differences, who created them, how Drupal supports them with modules, and key concepts like variables, mixins, and functions. It recommends that SASS will likely power Drupal 8's styling and provides additional learning resources.