I have been playing with the following website building content management systems,
A CMS (content management system) provides a skeleton site which can then be adapted to suit your needs. The style can be changed and functions can be added and removed. Most CMS have functions for adding users and storing user information and records. General systems like Drupal and Typo3 can be used to make sites with forums and blogs but lots of other features can be added.
Some CMS are built for a special purpose. Moodle is one of these. It provides a platform for online course management. Other systems exist for building online shops, blogs, forums, wikis and customer support.