Unlike standard trading on Steam, Trade Offers can be conducted without both friends online at the same time, and it's accessible via web browsers. Currently, the feature can only be used between Steam friends, but it may expand outside of these confines in the future. Users with their Inventories set to "private" will not be eligible to receive trade offers, Steam clarifies. In the Steam client, Trade Offers is listed in the Inventory tab.
Remember: One man's Level 5 Frying Pan is another man's treasure.