Drupal : Amazing CMS

Drupal is an open-source content management system(CMS). It's very flexible and useful to build websites with PHP files, MySQL and so on... It's worth using it for big websites!
If you want to start it, please read the articles on the websites below. The installation of Drupal may be long and complicated process for beginners.
https://drupal.org/documentation/install
http://www.siteground.com/tutorials/drupal/drupal_installation.htm