Categories enable you to group related content to help users navigate your web site. For example, if your site contains a large number of press releases, you can create categories like "News," "Sports," "Science," and so on, to enable users to list only items of interest. To display a list of categories for your web site users, add a Menu widget and select the menu. A content item can be assigned to any number of categories — there's no maximum.
You can create hierarchies of categories by defining parent categories. These hierarchies are appropriately indented when displayed, to help users navigate.