Trade is a module made to make trading relics easier. You can set a relic for buying (red) or selling (green), making you see who is buying it and selling it by pressing + and other players will see your buy or sell request as well. Players with a light name are in the room and players with a dark name are online but not in the room.
While some people trade relics for other relics, it's usually easier to use a currency to prevent bartering issues where no one has what anyone needs. As such most trades often involve cheese coins (cc) .