What is WordPress CMS. WordPress (WordPress.org) is a free and open-source content management system (CMS) based on PHP & MySQL. It is associated with blogging, but supports other types of web content as mailing lists, media galleries and online stores. It was released on May 27, 2003, by its founders, Matt Mullenweg and Mike Little. WordPress works with themes and plugins. Many years ago, WordPress was primarily a tool to create blogs Websites, rather than more traditional websites. Nowadays, thanks to changes to the core code, as well as a WordPress’ massive ecosystem of plugins and themes, you can create any type of website with WordPress.