Drupal is a Content Management System. That’s all. This site is built with Drupal. Stop. Many sites are built upon Drupal. Drupal won Best Overall 2008 Open Source CMS Award by Packt, consecutively for second year. Why? Because Drupal is simple, Drupal is elegant, and Drupal is powerful. If you are not that familiar with Drupal, you may look into its features at demo Drupal site. Also watch the following video to get an overview of Drupal CMS.
Drupal Overview: A nice video showing Drupal’s power
There is a full site, DrupalDojo.com, dedicated to Drupal learning. Many videos are there, and these easy to follow video tutorials will help you get started with Drupal soon. Here is another video to know the benefits of using Drupal.
CMS – Drupal Benefits
Good luck with Drupal!