I had this explained at Essen 2010 and it seemed like a neat game. A part of my Hey Waiter! deal.
Venice, the 1400's. You are a young merchant trying to make your name in this legendary port of vibrant commerce. Trade in spices, silks, gems, iron, and grain can bring great wealth... if you can bend the market to your will. Buy goods as they enter the city docks and sell them to the tradesmen who need them. Increase your profits by buying shares of the shops that use the goods in which you trade. Gain gold and prestige by fulfilling the orders of the Guild Hall craftsmen.
But Venice is a city of fickle demands and mercurial politics. Spend your ducats wisely and look for help from powerful people such as the Guildmaster, the Harbormaster, the Tax Collector... or perhaps a Thief. Even the humble Gondolieri have powerful connections in Venice. In the end, the most important thing to remember is the simple rule of commerce.