Joomla is a content management system (CMS) that can be used to build various types of websites, including corporate sites, magazines, e-commerce sites, and more. It features user management, media management, language support, banners, polls, search, and content creation tools. Joomla uses a modular framework approach with extensions, components, modules, templates, and libraries. To develop for Joomla, one would create components with an entry point, controller, model, view and template. Modules are developed with an entry file, helper, and template. Templates define the design and include necessary files.