You may have seen a "Hide" selection in the bulk actions drop-down menu. If you have items that you don't plan on listing or don't want crowding your view, then you can check to "Hide" them. This tool will hide the items from your view on your Amazon Inventory tab and will make managing your inventory a little more convenient.
If you want the hidden items visible again, simply select "Hidden" from the Archived filter on the Amazon Inventory Tab to see the items you have hidden. Select the items you wish to unhide from the drop down menu, then check "Unhide" and "Apply Action" to have the items re-appear with your other non-hidden listings.