Variables in SCSS allow you to assign an identifier of your choice to a specific value.
Why is that useful? Unlike in CSS, if you need to tweak a value, you'll only have to update it in one place and the change will be reflected in multiple rules.
$ is used to define and reference a variable:
Note: It's important to stick to one naming convention for variables when you first build out your codebase. This will help you reference them easily in the future.