Joomla! is a free and open-source content management system (CMS) and is one of the most popular website hosting software. According to the official website, Joomla! is built on a model-view-controller web application framework that can be used independently of the CMS, allowing you to build powerful online applications.
One of my personal favorites of Joomla! is the multi-language support with its large library of language packs. You can also translate the website admin backend with language extensions, helping you to easily localize your website.