The bottom line for Content Management Systems is managing content and publishing.
A content management system (CMS) is a computer software system for organizing and facilitating collaborative creation of documents and other content. A content management system is frequently a web application used for managing websites and web content, though in many cases, content management systems require special client software for editing and constructing articles.
CMSs are frequently used for storing, controlling, 'versioning', and publishing industry-specific documentation such as news articles, operators' manuals, technical manuals, sales guides, and marketing brochures.
The content managed may include computer files, image media, audio files, video files, electronic documents, and Web content. These concepts represent integrated and interdependent layers. There are various nomenclatures known in this area: Web Content Management, Digital Asset Management, Digital Records Management, Electronic Content Management and so on. The bottom line for these systems is managing content and publishing, with a workflow if required. —Wikipedia
San Diego Webmaster Services develops CMS websites using Open Source applications, like Joomla! and WordPress. These two systems can be now fully integrated via components that allow the interoperability of both systems. You can see an example here.