|This is a maintenance category. It is used for maintenance of the Wikipedia project and is not part of the encyclopedia. It contains pages that are not articles, or it groups articles by status rather than subject. Do not include this category in content categories.|
This is a hidden category. It is not shown on its member pages, unless the corresponding user preference 'Show hidden categories' is set.
This is a tracking category. It builds and maintains a list of pages primarily for the sake of the list itself. Pages are added to tracking categories through templates.