Joomla! is a free and open-source content management system (CMS) for publishing web content. ... It is built on a model–view–controller web application framework that can be used independently of the CMS that allows you to build powerful online applications.

What's a content management system (CMS)?
The definition of a CMS is an application (web-based), that provides capabilities for multiple users with different permission levels to manage (all or a section of) content, data or information of a website project, or intranet application.
Managing content refers to creating, editing, archiving, publishing, collaborating on, reporting, distributing website content, data and information.

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