The Trader does not have any crafts but allows trading between colonies. The trade menu is accessed from the colony settings menu, Diplomacy or by clicking on a trader job block. Trade between colonies will also work without any trader but every trader job increases the speed of trades.
At the trade menu the foreign colony has to be selected, it can be owned by the same Player or also a different one in multiplayer. Afterwards the item has to be selected and the limits of the trade. For the number of trades 1.000.000 (default value) means unlimited. Trades can be set up only by the sender colony.