A category in Joomla groups content within a particular component. Article categories form a tree of sections and subsections.
How the structure works
A com_content article belongs to one category, and a category may have a parent. Contacts, banners and third-party components can maintain their own category trees. Categories from one Joomla component do not automatically categorise another component’s records. Modules normally use other organisational tools.
Using categories
Plan a clear hierarchy, then configure publication, language, access and display options. A Joomla menu item can show a category blog or list. Uncategorised is an initial category that can be renamed and configured like other categories.
Use categories for structure and tags for additional overlapping classifications. Check routes and display settings when changing a Joomla category tree.