WordPress is one of many PHP/MySQL content management systems that allow content editors to use a web interface to maintain their sites instead of editing and uploading HTML files to a server. Some systems, like Movable Type and Text pattern, have reputations as good blogging platforms. Others such as Joomla, Drupal, and Expression Engine are more commonly associated with commercial or community sites.
WordPress began as a blogging tool, but early on the developers added pages as a separate content type. This opened the door for people who didn’t want a blog, but did want an easy, web-based interface to create and manage web content. (And if they later decided they needed a blog after all, the world’s best was just one menu click away!) Since then, the page features have evolved. Whether WordPress acts a blogging tool or a true content management system, then, depends on which content you choose to emphasize in your site.