Content management system (CMS) is a data-storage system with several functions.  It allows users to: collect, maintain, and publish information; to manage content lifecycles (versions, archives); to manage access to content by appropriate users; and to route tasks such as content creation or approval) among users as appropriate. 

When used for a website, it allows users to publish a single piece of web content to all the pages where it should appear, eliminating duplicated effort and inconsistent information.  It also provides customizable templates, which control consistency in look-and-feel and navigation, and also eliminate the need for users to create pages from scratch.