A content management system (CMS) is a system used to manage the content of a Web site. Typically, a CMS consists of two elements: the content management application (CMA) and the content delivery application (CDA). The CMA element allows the content manager or author, who may not know Hypertext Markup Language (HTML), to manage the creation, modification, and removal of content from a Web site without needing the expertise of a Webmaster.

A Normal non-CMS Website creates a bottleneck between Webmasters i.e. website developers and website owners  or administrators. They have to be dependent on developers for every contents,images updates, addition and changes. This is explained in an image shown below:

Whereas a CMS has much more benefits than a regular website. Working style of CMS is shown in below image:

Key Benefits of CMS :

• allows non-technical staff the ability to update web site content without knowing HTML, FTP, etc.
• easy-to-use WYSIWYG tools, similar to Word (code view as well)
• workflow / approval -- can be as complex or as simple as desired
• each unit decides on the workflow that best meets their needs
• individuals who have natural responsibility for content can maintain that content themselves (with approval process if desired)
• consistent visual identity (CLF)
• standards-based code
• archiving / backup / recovery
• turnover and succession planning
• content more likely to be kept up-to-date (review reminders)
• information more easily found
• more cohesive user experience
  makes site maintenace and (re-)development easier and far less costly
• web professionals are freed to focus on higher-value tasks, i.e. developing interactive functionality, improving site usability