Help:Categories/Create a Category
A category can be created the same way as other wiki pages (See Help:Starting a new page); just add "
Category:" before the page title. (Category lists exist even if their description page is not created, but these categories are isolated from others and serve little purpose for organization or navigation.)
It is not possible to rename (move) a category, unlike other wiki pages. It is necessary to create a new category and change the Category tag on every page. The new category will not have the older category's page history, which is undesirable if there are many revisions.
To avoid extra work, try searching within your wiki before creating a new category. The list of all categories can be found in "Special pages" in the "tools" box of the sidebar.