WordPress is a free and open-source content management system that can be used to build blogs or websites. It runs on PHP and MySQL and is used by over 34% of websites globally. There are two main versions: WordPress.com which provides free hosted websites with limited customization, and WordPress.org which allows fully customizable self-hosted websites but requires your own web hosting. Building a basic WordPress.com website requires an email, web browser, content ideas, and use of themes and plugins for customization within WordPress' limitations for the free version.