WordPress is a free and open-source content management system (CMS) used for creating websites and blogs. WordPress provides users with a wide range of templates and themes that can be customised to create unique designs for websites. It also includes a built-in editor that allows users to create and publish content easily, and a plugin architecture that enables developers to create custom functionality for WordPress sites. The CMS is a popular choice due to its ease of use and flexibility, making it the ideal basis for website development projects.