Archiving your QA pairs allows you to remove content from your active library without having to fully delete it. This will help preserve any valuable data that was attached to that content.
It's important to note that you're free to archive and unarchive your content as much as you'd like, so if you're not sure whether a QA pair is valuable to your organization, archiving it will keep it safe and accessible while you make that decision. This video will walk you through how to archive your content.
You can also consult the Help Center, or Responsive University for more info on this helpful feature.