A SASS file is a Syntactically Awesome StyleSheets file. It contains Sass syntax, which is an extension of cascading style sheets (CSS) used to format the layout of webpages.

CSS can be used to define text styles, table sizes, image appearance, and other aspects of a webpage. Sass provides capabilities that build upon CSS functionality to help users work more effectively with their stylesheets. However, the Sass language is not intended to replace CSS, as web browsers cannot interpret SASS files directly. Instead, SASS files can be compiled into CSS files that are then used to format the contents of webpages. The Sass language consists of two syntaxes: Sass - The original syntax that uses indentation instead of brackets for indicating nesting of selectors and newlines in place of semicolons to separate properties. This syntax is used by SASS files. Sassy CSS (SCSS) - A superset of the original Sass syntax and is more commonly used. It extends CSS functionality by providing mixins, nested rules, variables, and inline imports. Sassy CSS files are saved with a .SCSS file extension.