WordPress is a open-source CMS (Content Management System), and the platform of choice for over 30% of all sites across the web. WordPress is built on PHP and MySQL and started off as a blogging platform from which is has evolved into a powerful and flexible tool to build amazing websites on.
It comes with core functions out of to box for content management, e.g. adding and editing pages and posts. These posts types can be extended or added to, giving you the flexibility to build anything from a simple blog, a company brochure website, to a complex integrated multisite showing regional content across the globe.