Archived Milestones & Tasks?

Archived Milestones & Tasks?

At the far right of the page-specific menu bar on the Tasks & Milestones page of an active project is the word "ARCHIVED" and it is a link that goes to a page called "Archived Tasks & Milestones". Once there the link changes to "Active Tasks & Milestones" and returns me to the regular Tasks & Milestones page of my project.

Since there already is a way to archive whole projects and another link to view them, this link doesn't seem to be related to that. So...

What is this link for? How is it used? I can not find any way to "archive" a particular Task or Milestone within a project (though I sure would like to!) but this link seems to indicate that there SHOULD be a way to do it.

What am I missing?

Thanks very much,
Buck