What is the different of CSS, SCSS, and LESS?

Answer 1

https://responsivedesign.is/articles/difference-between-sass-and-scss/

Answer 2

SCSS and LESS are CSS preprocessors. Basically pre-processors allow you to make use of features that are not present (or are present, but without full support between browsers, as is the case of variables) and then generate a traditional CSS file (and totally valid). Some also have a much clearer syntax (this is relative to the programmer)