Drupal is a free and open-source content management system (CMS) that allows users to build and manage dynamic websites without needing knowledge of PHP. It can be downloaded and installed on a web server that supports PHP, MySQL, and cron jobs. The document outlines how to install Drupal, including extracting and uploading files, creating a MySQL database, and configuring settings.php. Additional configuration steps after installation include setting up modules, themes, and other site options.