Drupal is...
Drupal is a web content management system (CMS). That is, it's a toolfor creating, editing, organizing and publishing website content. Thisdocument covers aspects of Drupal within the context of PortlandState's multi-site implementation, but you can learn a lot aboutDrupal's history and technical features at drupal.org.
Using the web to manage a website
Drupal operates in a web environment and thus doesn't require anysoftware installation beyond a web browser. Think of it as a website tomanage your website(s).