A map is a set of from → to pairs that allow you to do things like check if a URL has "/blog/" in it (the "from") then it is a "Blog Post" (the "to"). Rules can be more sophisticated like "if it's a Blog Post and over ten years old then delete it". This is a way to categorize content very quickly and efficiently (and also allow you to reiterate often).
Chimera allows you to define, manage, and run maps and rules.