CMS became a buzz word in the web development industry because of its benefits.
CMS stands for Content Management System. It is a term and has not been endorsed with a solid definition. A CMS can have multiple meanings depending on the scenarios and the person's or project objectives.
To add to the confusion, an organization named AIIM (Association for Information and Image Management) claimed the acronym ECM (Enterprise Content Management) and WCM (Web Content Management) as their creation and came up with their own definition that suites their organization's services. AIIM changed their definition of ECM a few times and submitted their definitions to Wikipedia, which is now published.
At the time of this writing, for most scenarios, when someone in the web development industry is talking about CMS (Content Management System), or ECMS (Enterprise Content Management System), he / she is more likely referring to either the first or second definition below.
In this article, I'll put the emphasis on the common CMS definitions and not the one created by AIIM. The detail of the purpose, use, and examples are all in the area of the commonly used definition.