from http://drupal.org/about

General information about Drupal

A
dynamic web site platform which allows an individual or community of
users to publish, manage and organize a variety of content, Drupal
integrates many popular features of content management systems,
weblogs, collaborative tools and discussion-based community software
into one easy-to-use package.

As an open source software project maintained and developed by a community, Drupal is free to download and use. If you like what you learn here, please work with us to expand and refine Drupal to suit your needs.

A wide range of site configurations

By enabling and configuring individual modules, an administrator
can design a unique site, one which can be used for a combination of
knowledge management, web publishing and community interaction
purposes. So that you can better understand the many possibilities, the
following list of features have been organized by common web platform
characteristics:

• Content management. Via a simple, browser-based interface,
  members can publish to a number of available content modules: stories,
  blogs, polls, images, forums, downloads, etc. Administrators can choose
  from multiple theme templates or create their own to give the site a
  singular look and feel. The flexible classification system allows
  hierarchical classifications, cross-indexing of posts and multiple
  category sets for most content types. Access to content is controlled
  through administrator-defined user permission roles. Site pages can
  display posts by module type or categorized content, with separate RSS
  feeds available for each display type. Users can also keyword search
  the entire site.
• Weblog. A single installation can be configured as an
  individual personal weblog site or multiple individual weblogs. Drupal
  supports the Blogger API, provides RSS feeds for each individual blog
  and can be set to ping weblog directories such as blo.gs and
  weblogs.com when new content is posted on the home page.
• Discussion-based community. A Drupal site can act as a
  Slashdot-like news site and/or make use of a traditional discussion
  forum. Comment boards, attached to most content types, make it simple
  for members to discuss new posts. Administrators can control whether
  content and comments are posted without approval, with administrator
  approval or through community moderation. With the built-in news
  aggregator, communites can subscribe to and then discuss content from
  other sites.
• Collaboration. Used for managing the construction of Drupal,
  the project module is suitable for supporting other open source
  software projects. The wiki-like collaborative book module includes
  versioning control, making it simple for a group to create, revise and
  maintain documentation or any other type of text.