What is CMS and any relation its with wordpress, Joomla, Drupal

[hooda]

Dear All,
I want to know what is CMS ?. Where it is used for. do i know Wordpress, Drupal, Joomla its part of CMS.
Thanks

[HenryWilson]

A content management system (CMS) is the collection of procedures used to manage work flow in a collaborative environment. Wordpress, Drupal, Joomla are the different types of content management systems.