Sale by Tender is like a silent auction. The house is displayed for sale without a price or with a price guide only and a due date for all the offers. During that time interested parties put in offers and conditions which are sealed in envelopes and all presented on one day in front of the vendors. The sellers then go through the offers, and choose the one they want to accept
The benefits for the vendor is that marketing without a price targets, all buyers and can generate a lot of different offers because everyone needs to submit their best offer at tender.
Some purchasers like this way of buying because their bids are confidential and it can also prevent them from bidding too high when they are competing against other bidders in an auction.