A Web Content Management System (WCMS) -- or more popularly referred to as simply a CMS -- is a software system that provides website authoring, collaboration, and administration tools designed to allow users with little knowledge of web programming languages or markup languages to create and manage website content with relative ease. A robust WCMS provides the foundation for collaboration, offering users the ability to manage documents and output for multiple author editing and participation.
Most systems use a database to store page content, metadata, and other information assets (i.e. pictures, videos, audio files etc.) that might be needed by the system (aka the Web site).
A presentation layer displays the content to website visitors based on a set of templates or in the case of Wordpress, a “theme.”
A WCMS allows non-technical users to make changes to a Web site with little training. A WCMS typically requires a systems administrator and/or a web developer to set up and add features, but it is primarily a website maintenance tool for non-technical staff.