"Content" publishing is perhaps the broadest term for the publishing of anything at all. The "content" of a publication can be words, video, audio, still images, -- theoretically, anything that the five human senses can detect. "Content" is a generic term used to indicate anything which fills the emptiness in between advertisements in magazines, news broadcasts, and other mass media. "Content" is a Web designer's term for "things I don't really pay any attention to but which I'm told to insert here." So much for the creative beauty of writing and art.
Content management is the complex process of creating, displaying, archiving, search, and retrieval of content. A newpaper's web site, for example, contains thousands of articles which must be displayed on certain days and on certain pages of the site. Visitors must be able to search for articles by keywords. Once the news is old and no longer news, it must still be stored and made available for search and retrieval. Most importantly, the content must be displayed along with the ads that pay for its production and content management, in a manner that makes the content readable but doesn't interfere with the advertising's attempt to get the reader's attention. Content management publishing is a technical craft, not an art.
Content publishing software helps to automate much of the content management publishing process. Content words are indexed by the software for easy searching. Content itself is stored in a file system that is indexed to a database of keywords, dates, and events that trigger the movement of content from "online" to "archived offline" and so on. Content publishing software can also determine which ad(s) are displayed along with which content, and how often each ad is displayed.
Wordpress is a popular example of content publishing software used for blogging. Using prefabricated "themes" or screen layouts, an author can concentrate on writing words while the software determines how they are displayed. Ads and other ancillary objects can be inserted into blog posts. A piece of content, called a "post" in Wordpress, can be tagged with words and grouped with other posts of similar tags; thus, you can have a list of categories such as "Book Printing" or "Online Publishing" that people can click in order to view posts that are about a specific topic. This is just one example of what content publishing software can do.