Definition
WordPress is an open-source content management system built on PHP and MySQL that powers roughly 40% of all websites on the internet. Self-hosted WordPress, downloaded free from wordpress.org, installs on any PHP and MySQL compatible hosting account you control entirely; WordPress.com is Automattic's hosted version, billed monthly, where server management is handled for you but customisation is more limited. Around the open-source core sits a managed WordPress hosting industry, including Kinsta, WP Engine, Pressable and Flywheel, that tunes servers, caching, security patching and core updates specifically for WordPress so site owners avoid general system administration. A global ecosystem of plugins, themes and developers makes it the most extensible CMS in mainstream use, though that flexibility means quality and security vary plugin by plugin. It suits content-led sites, blogs and small stores well; for highly custom applications or teams wanting zero server involvement, other platforms may fit better.
How it works
WordPress is PHP and MySQL: a content editor and admin in the browser, a theme system for design, a plugin system for functionality, and a REST and GraphQL API for headless use. Modern WordPress also supports the block editor (Gutenberg) and full-site editing.
Why it matters
For content-led sites, blogs, brochure sites, magazines, small e-commerce stores, WordPress is the default and remains hard to beat on cost, customisation and ecosystem. The trade is the operational burden of updates, security and performance, which is why managed WordPress hosting exists.