This is a maintenance category, used for maintenance of the Wikipedia project. It is not part of the encyclopedia and contains non-article pages, or groups articles by status rather than subject. Do not include this category in content categories.
This is a tracking category. It builds and maintains a list of pages primarily for the sake of the list itself. They are not part of the encyclopedia's categorization scheme.
Pages are added to this category by Template:Commons category. It tracks cases where we have a locally defined link to Commons, and it's the same as Wikidata.