A content management system is software which provides website authoring and administration tools designed to allow users with little or no knowledge of web programming to create and manage the site's content with ease while maintaining professional looking, search engine friendly output. This means you pay a one-time setup cost, and then update the site according to your schedule and needs, without paying a webmaster to add your new information.
Most systems use a database to store content, metadata, or artifacts that might be needed by the system. A presentation layer displays the content to website visitors based on a set of templates (themes) that usually allow for impressive graphic design and a very professional look and feel both on computers and mobile devices.
Adding and updating content is typically done through browser-based interfaces, so you can comfortably use any operating system and any browser. Unlike web “site builder” applications, a website CMS allows non-technical users to make changes to a website.