What is a CSS Authoring framework?

I were looking for a CSS Framework to help me built website, when I struck with Compass.

Now, while I understand what a CSS Framework is, I don't understand what's a CSS Authoring Framework.

Expecially, I don't understand if it "replaces" a CSS Framework (like blueprint) or you should use it with a CSS Framework.

I'm building a website using Ruby On Rails, and I use SASS but no CSS Frameworks at the moment. If anyone can point me in right direction after answering the question, it will be really appreciated.

Edit 1: Also, which is the difference between a CSS Framework and a CSS Authoring Framework