Syntactically Awesome Stylesheets (SASS) is a powerful preprocessor scripting language that is interpreted or compiled into Cascading Style Sheets (CSS). SASS extends CSS with features like variables, nesting, mixins, inheritance, and functions, making stylesheets more maintainable, organized, and dynamic. The primary file extensions associated with SASS are '.scss' (the newer, CSS-like syntax) and '.sass' (the older, indented syntax). While 'syntacticallyawesomestylesheets' is not a standard file extension itself, it directly refers to the SASS language. These files contain code that must be compiled into standard CSS before a web browser can interpret them for styling HTML and XML documents. This compilation process allows developers to write complex, reusable styling logic that is then flattened into the universally understood CSS format for deployment.