Market
List items straight from your ladder characters and shared stash, and make offers for other players' items. You hand items over in a game, or with an instant trade: for a price in runes, the server moves the item from wherever the seller keeps it (shared stash, a character or the mercenary) into your shared stash and the runes from your Runes tab to theirs, once you both have closed the game. A listing closes by itself once the item is gone from your saves, unless you agreed on a trade: that stays up until one of you marks it done, at most 24 hours.
Your listings
Your offers
Instant trades happen only while both players have D2R closed. Play the ladder through the launcher as usual: when you close D2R, it uploads your saves and tells the server you're out. The trade then runs on the server, so the launcher doesn't have to stay open, and your next Play ladder brings the item and runes into the game. Players who are online show a green dot: whisper them right from the listing, or copy a whisper for the chat in the game.
Trade fair. Without an instant trade, the seller hands the item over in a game once you agree. Accepting an offer tells the buyer to whisper you. An agreed trade stays on the Market until one of you marks it done, at most 24 hours. Scams can be reported to an admin with /report in chat.