Tenders are sealed bids that are submitted directly to the seller. The seller will then pick the winning bid at the end of the sale. All tenders end at the same time. Buyers do not see any other offers that have been made. Buyers can submit more than one bid but can not withdraw a bid once it has been submitted. All lots will end at the same time.
Auctions are a sale where equipment is awarded to the highest bidder. Buyers can submit bids up to the deadline of the auction. Some lots may be extended through the bidding process. The bids are open so buyers can see what the current highest bid on the equipment they are bidding on.