What Was Compass?
Compass was a CSS-Authoring framework for Sass. It provided Sass mixins and other functionality that helped you kickstart a website quickly. For full details, see the official documentation.
Compass is no longer actively developed. You should not use it for new projects. Consider TailwindCSS or Bourbon instead, which are also part of CodeKit.
Compass was end-of-lifed in 2016 and CodeKit has maintained support for it for 5+ years. This support will be completely removed in a future version of CodeKit, so you should migrate your old Compass projects to a modern framework.