What does it mean to archive a smartURL?

Archived smartURLs are simply removed from your list, to reduce clutter. For people clicking on a smartURL, it makes no difference whether it is archived — the smartURL will take them to their destination regardless. Archiving a smartURL is for your view only, so if other users have access to that smartURL, it will still appear in their Current smartURLs list. It is impossible to delete a smartURL.