This is the ability to have users submit content to the web site online. It creates the content but does not publish the content to the live web site unless the user has the priviledges to do such. It further allows for a publication process where a reviewing can act as an editor prior to the release of the content to the public web site.
A good way to think about the system is a writer submits content. The content is reviewed by either a reviewer or the manager. The content can be approved for publication or declined.
This allows all users to help maintain the web site. However, it also reduces the work load of staff to produce the content for the site.