In a nutshell, Rules is a visual programming tool. Instead of writing code as a block of text, you configure the desired behavior via a GUI that guides you through the setup of "rule sets" which are basically stored procedures that define conditionals and actions to execute, and triggering those rulesets from various canned events.

Rules sets can can call each other immediately (watch out for infinite loops), schedule each other (or themselves) to be called later, etc.

When I was developing Cloudtask, I discovered none of the interfaces in the Python multiprocessing module were powerful enough for my needs so I had to roll my own. The result is the generically useful multiprocessing_utils module in turnkey-pylib which from my totally subjective perspective provides a far superior interface to parallelization than the built-in multiprocessing interfaces.