A content management system (CMS) is a collection of procedures used to
manage work flow in a collaborative environment.
It allows:
http://drupal.org/
http://wordpress.org/
http://info.tikiwiki.org/tiki-index.php
http://typo3.org/
http://www.mediawiki.org/wiki/MediaWiki
Which CMS to choose?
http://en.wikipedia.org/wiki/Content_management_system