Sass (the preprocessor) allows two different syntaxes: SCSS (a CSS-like syntax) and Sass (indented syntax).
The new main syntax is “SCSS”, is a superset of CSS3’s syntax. This means that every valid CSS3 stylesheet is valid SCSS as well. SCSS files use the extension .scss
Sass, the older syntax indented syntax is intended for people who prefer conciseness over similarity to CSS. Instead of brackets and semicolons, it uses the indentation of lines to specify blocks. Files in the indented syntax use the extension .sass