Let’s talk about drupal.
Drupal is a free and open-source content management framework written in PHP and distributed under the GNU General Public License. It is used as a back-end framework for at least 2.1% of all websites worldwide.ranging from personal blogs to corporate, political, and government sites including whitehouse.govand data.gov.uk. It is also used for knowledge management and business collaboration.
The standard release of Drupal, known as Drupal core, contains basic features common to content management systems. These include user account registration and maintenance, menu management, RSS feeds, page layout customization, and system administration. The Drupal core installation can be used as a simple website, a single- or multi-user blog, an Internet forum, or a community website providing for user-generated content. To work with drupal, you should start from the Wikipedia page , there are a lot of basic concepts given about drupal.
Current drupal version is 7.23, it has about 23945 registered modules and 1847 themes . Drupal has a healthy documentation available in .
If you are interested, download and start reading this (https://drupal.org/documentation/install)