What is Content mangement for a webpage?

http://en.m.wikipedia.org/wiki/Content_management
Content management, or CM, is the set of processes and technologies that support the collection, managing, and publishing of information in any form or medium. When stored and accessed via computers, this information has come to be referred to, simply, as content or, to be precise, digital content. Digital content may take the form of text (such as electronic documents), multimedia files (such as audio or video files), or any other file type that follows a content lifecycle requiring management.

http://en.m.wikipedia.org/wiki/Content_management_system

The core function and use of content management systems is to present information on websites. CMS features vary widely. Simple systems showcase a handful of features, while other releases, notably enterprise systems, offer more complex and powerful functions. Most CMS include Web-based publishing, format management, revision control (version control), indexing, search, and retrieval. The CMS increments the version number when new updates are added to an already-existing file.

A CMS may serve as a central repository containing documents, movies, pictures, phone numbers, scientific data. CMSs can be used for storing, controlling, revising, semantically enriching and publishing documentation.