We make use of views and panels quite often in Drupal and a lot of people are utilizing CTools in development. I can't find a lot of documentation on what it is and why you'd use it and the drupal.org forum isn't providing much either.
What is CTools, and is it worth using? What is the best use-case for utilizing it?
The Chaos Tool suite is just a set of API's for a better developer's experience. In short, it spices up things and makes it easy to customize some components of Drupal.