The Open/Close Bidding page lets you quickly open or close bidding on selected items.
If you are using online, or Kiosk Mode, bidding then all bids on an item are recorded, not just the winning bid. Bidding on the item will stay open until the closing time of either the item, or the auction.
When you Record Bids, from the Bidding/Sales page, you can control whether or not the bidding is closed for the item using the Final Bid checkbox.
If you enabled online pre-bidding for silent auction items, bidding on the silent auction items will not automatically close. If there were no further bids recorded against the silent item during the event, you will need to manually close the bidding. This can be done on the Item Details page and/or for all items from this page.