Template:TemplatePAGENAME/doc
 | This is a documentation subpage for Template:TemplatePAGENAME. It may contain usage information, categories and other content that is not part of the original template page. |
{{TemplatePAGENAME/doc}} inserts the name of the template currently being documented. It is equivalent to either {{PAGENAME}} or {{BASEPAGENAME}} depending on whether the currently viewed page is the documentation subpage or the template itself (which presumably transcludes the documentation subpage via {{template doc}}).