Drupal is a free and opensource Content Management System which is used for building Websites. It is based on LAMP Architecture using PHP as implementation language. You can read success stories from the website and from the author Dries Buytaert ‘s personal blog. Most of the success of Drupal derives from his modular architecture which simplifies development, collaboration and user contribution. Drupal’s history can be read here.
Bird’s eye view of Drupal architecture can be sketeched by following diagram:
Read more: Enjoythe architecture