WordPress is a popular open-source content management system (CMS) that allows users to create, manage, and publish websites or blogs. It is well-known for its user-friendly interface, extensive theme and plugin ecosystem, and flexibility for customization. WordPress is available as a hosted service at WordPress.com, which offers features like custom domains, premium themes, and priority support with different subscription plans. For tech-savvy users, WordPress software can be downloaded from WordPress.org for self-hosting and greater control over site customization.