This category is the mother of all categories. In other words, all categories on GuildWiki should be subcategories of this one. Any category listed here should not have be listed in any other categories - if it is, then there is no reason for it to be in this category.
You can use it to help you find a proper category for your page - just drill down until you can't find a more specific category that fits.
See also: Category Tree
This category is the only category in Special:UncategorizedCategories.
This category has the following 15 subcategories, out of 15 total.