For the Trader Role, players are allowed to sell a single good that they have produced for some amount of money. This is done through the trading house, which is pictured below.
The trading house only has room for 4 barrels of goods. Once someone trades the fourth good, the trading house is full, and nobody else may trade anything for thus turn.
In addition to that, the trading house only wants 1 of each type of good. In the picture below, the trading house contains coffee, sugar and corn. Because of that, nobody may sell corn, sugar or coffee on this trading round.
The trading house card shows the base price for the good that you are selling. This is how many dubloons you get when you sell a good of that type. If you are the person who chose the Trader role, then you get 1 additional dubloon.
Starting with the person who picked the Trader role, each player in turn is given a chance to trade, if they are able. After everyone has had a chance to trade, if the trading house has 4 goods in it, then they are cleared out. Otherwise, they remain.
Like many of the other roles in the game, picking the Trader role allows you to directly control what other players can do. If you see that most people have sugar, for example, you can pick trader and trade sugar, which stops anyone else from being able to trade sugar at all.
