WordPress is an open-source CMS (content management system: software that stores a site's pages and posts in a database and lets people edit them in a browser) and publishing platform. A worldwide community of contributors builds it in the open; the WordPress trademark belongs to the WordPress Foundation.
WordPress runs on PHP and stores content in MySQL or MariaDB. The project recommends a host with PHP 8.3 or later, MySQL 8.0 or MariaDB 10.11 or later, and HTTPS, with a web server such as Apache or Nginx. Pages are built in the block editor, which shows the page as it will look while content is added, edited and moved. Themes set the design, and block styles can be changed for each screen size without CSS. Plugins add functions such as a store, analytics, a newsletter or social media integration. The home page presents WordPress 7.1 as the current version.
WordPress is free software under the GPLv2 (or later) license, and plugins and themes, as derivative works, inherit that license. The software costs nothing; a site needs a web host, and the project lists hosting companies on its hosting page.