I'm not sure if you mean just listing a domain for sale or selling in auction but maybe some of this will help ?
Off sedo's website
Normal listing a domain at sedo for sale
In order to provide you with maximum flexibility when negotiating your sales, we offer various pricing options which you can assign to each of your domains. The options are as follows:
Minimum offer: Once you have entered a minimum offer, any offers below that amount are automatically rejected by the system. In this case, interested parties are encouraged to make another, higher bid.
Asking Price: The price you enter is used as a basis for negotiation. You are not obliged to sell at this price. If you do not enter a price, your domain will be listed as 'Make Offer'. All offers received are passed on to you by email.
Fixed Price: Offers are only accepted if they match your exact price.
You are however legally obliged to accept this offer! Should you decide to set a fixed price, please enter the fixed price in the ‘Asking Price’ field and type the letters ‘FP’ in the ‘Minimum Offer’ field.
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What is the difference between Marketplace Auctions and Brokerage Auctions?
In Marketplace Auctions the reserve has already been met at the start of the auction, while in Brokerage Auctions the reserve has not been met when the auction starts.
A Marketplace Auction is an auction that is initiated by the seller
once he has received an offer through Sedo’s traditional marketplace, and this offer will
serve as the reserve price for the auction. Since you already have a committed offer at the reserve price, your auction listing is guaranteed to end in a sale!
Sedo offers an auction program for premium domains where the domain owner will work in coordination with a Sedo broker to determine the reserve and start and auction for the domain. For brokerage auctions the reserve is not met from the start of the auction and a sale is only guaranteed if the reserve is met through the auction. The reserve is not listed on the auction page until it has been met.
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Hope this explains some of it for you
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