using the term "content management system" to describe the drupal cms understates it's full potential. i prefer to consider drupal a web-application development-system, particularly suitable for content-heavy projects.
what are the fantastic four?
drupal's application development potential is provided in large-part by a set of "core" modules that dovetail to provide an application platform that other modules and applications build on. these modules have become a de-facto standard: drupal's fantastic four. our superheros are cck, views, panels and cck field types and widgets. if you are considering using drupal to build a website of any sophistication, you can't overlook these.