SASS is a programmable approach to stylesheets which really adds some cool features. It can make a stylesheet easier to read, easier to update and also adds some powerful features like functions, variables and imports. (See http://sass-lang.com/docs/yardoc/file.SASS_REFERENCE.html for more details.)
This plugin enables any WordPress Theme to use SASS stylesheets. In a wordpress theme, the comments at the top of style.css are used to define the theme. For this reason, this plugin will not allow a .sass or .scss file named ‘style’.