WordPress is an open-source content management system that allows users to create and manage blogs and websites. It is used by millions of sites and seen by tens of millions daily. WordPress is free to use and open-source, meaning the source code is accessible and it can be modified and redistributed freely. There are two main versions: WordPress.com which is hosted, and WordPress.org which is self-hosted and has more customization options. WordPress uses a dashboard to administer sites and allows users to add plugins and themes to extend its functionality.