A content management system or CMS is a software that facilitates creating, editing, organizing, and publishing content. WordPress is a Content Management System, that allows you to create and publish your content on the web. Although it is mostly used for web publishing, it can be used to manage content on an intranet, or in a single computer.
Content Management Systems are web-based applications that are designed for the creation and updating of websites. They may have themes or plugins to extend functionality, and make the management of a website simple.