The listing gets approved. Sellers can browse the listings and make an offer to sell the item to the buyers. The sellers remain anonymous to everyone but the potential buyers. An e-mail is sent to the potential buyer of an offer that is made by a seller. Other potential sellers can view the offer, but not who the seller is, and may submit offers of their own.
Buyers can contact sellers who place an offer in their listing.
No other user will have access to the sellers contact information. Once the listing is closed, the buyer gets all the offers and sellers contact information. There is never any obligation to buy. Check the status of all your bids. This page will list your bids for all lots, and tell you whether it is a winning bid or a non-winning bid.