What is Drupal?
A concise definition of Drupal is difficult to come by, as many people use Drupal for many different things. The following definitions provide an incomplete cross section of how different people use Drupal (our working definition is the final one in the list):
Drupal is a database-driven web application written in PHP.
Drupal is an open source Content Management System (CMS) freely available under the GNU General Public License (GPL).
Drupal is a community-building platform.
Drupal is a web development framework. You can use Drupal as a platform to build a broad range of web applications.
Note
The previous definitions, however, can also benefit from further explanation. For those interested in additional reading and background, the following links provide a more detailed overview and some background information:
For PHP, visit http://php.net/.
For web content management system, visit http://en.wikipedia.org/wiki/Web_content_management_system.
For GPL, visit http://www.gnu.org/licenses/licenses.html. Drupal is covered under Version 2 of the GPL: http://www.gnu.org/licenses/gpl-2.0.html.
For web development framework, visit http://en.wikipedia.org/wiki/Web_application_framework.
For background information on open source, visit http://www.opensource.org.
For the overview section from the Drupal handbook, visit http://drupal.org/documentation/concepts.
Our definition: Drupal is a tool that helps people build interactive websites. It is free to download, install, customize, and use.