A Vickrey auction is a type of sealed-bid auction. Bidders submit their bids without knowing the bid of the other people in the auction. The highest bidder wins but the price paid is the second-highest bid. For example, if you bid 10 HNS for crypto/ and someone else bids 5 HNS, you'd win the auction and only pay 5 HNS for crypto/. This means that you don't spend more HNS than you need to when you win an auction.