Preprocessors (aka precompilers) can make your life much easier by eliminating code repetition and providing all sorts of yummy time-saving and code-saving features. If you’ve been using Rails, you’ll be familiar with SASS already since it’s baked in. If you’re not using Rails, you may need to add some additional steps to your workflow to get your preprocessor set up but it’s worth it.
This section contains helpful links to other content. It isn’t required, so consider it supplemental for if you need to dive deeper into something.