A Dutch auction is an auction of 2 or more identical items. All winning bidders pay the same price, which is the lowest successful bid. For example, if a seller has 3 of a particular item available, and the bidding goes like this:

Bidder A, 30 - winning
Bidder B, 30 - winning
Bidder C, 28 - winning
Bidder D, 24 - loosing
Bidder E, 22 - loosing

Bidders A, B, and C will get the item for 28, the lowest successful bid.
Proxy bidding is not used on Dutch auctions.