From Fedora Project Wiki
This template is used for release validation testing category pages. It can be used either for a milestone category, e.g. Category:Fedora 21 Beta Test Results, like so:
{{Validation results milestone category|release=21|milestone=Beta}}
or for a release category, e.g. Category:Fedora 21 Test Results, like so:
{{Validation results milestone category|release=21}}
The use of #if in the template makes it behave appropriately in either case (showing or not showing the milestone name, and adding the page to the appropriate category).