SCSS means Sassy CSS, because it’s exactly the same language as SASS (Syntactically Awesome Style Sheets), except that it uses a syntax that’s closer to the language it compiles into: CSS.
It has loads of advantages, but the main one is that a SCSS file of a few hundred lines can generate tens of thousands of CSS ones.
It has a few downsides too, for example, it has to be precompiled, and it doesn’t particularly do it well either, which can be a problem.
I recently discovered that the new tool I’m using, TailwindCSS, can do the same, but with better results, and without having to use two different tools for the same job.
That’s about it.