Drupal is an open-source Content Management System (CMS) which is particularly suited to customization through use of blocks, themes and modules. Drupal's innovative use of taxonomy and its unique menu system allow for effective management of content as a site grows or evolves.
With Drupal we can easily setup a blog, but we can also set up many more things, just from looking at Drupal sites we can designed: community with blogs and forums, calendar, ecommerce, magazine, corporate site, image gallery, intranet app to manage docs. Driving the on going development of Drupal is the desire for a simple and powerful framework which developers can work within to create custom web applications without having to build the pieces that nearly all websites have as a foundation (user authentication, content creation interface, layout management).
Unlike other similar CMS's, Drupal takes its role as a framework very seriously. Take a look at the database structure of any other CMS that has been around for a while, and you'll almost certainly find a labyrinth of tables with mysterious names and seemingly redundant purposes. Drupal's database design is clean and constantly being re-factored. Tables that have outlived their purpose are removed from the schema and the code. Table design is very generic, allowing different types of content and modules to share the same table space.
Drupal is a free software package that allows an individual or a community of users to easily publish, manage and organize a wide variety of content on a website. Tens of thousands of people and organizations have used Drupal to power scores of different web sites, including Community web portals