This is the "top-level" category*, intended to include all categories that would otherwise have no logical "parent". Each except the top one should be in a relevant parent category, and most low-level categories should have two or more parent categories. See: the Starter Pages Wikia for an indication of how most Wikia sites organise their top levels of categories.
*with the exception of Wiki, which is for uncrowded access to the most important broad subcategories.
This category has the following 6 subcategories, out of 6 total.