Any gamer in Rulers of the Sea can buy goods at the port market, sail to another port and sell them. Buy low, sell high. Gamers can even buy goods, store them in a warehouse at a fee, and sell them later on the same market. This is simple trading.
For businesses that produce goods this is different. They can sell their produce at the port market where the business is established, but they may rather want to sell it at a different port market where the goods are rare, or even deliver it directly to different business for another production process. For this they need to ship the goods overseas.
Shipping of goods is always possible because npc (computer operated) shipping companies have enough capacity. However, their shipping fees are high. Gamers that are in the shipping business can charge a much lower fee, and that way can take a large part of the of market. They might also lose less cargo to the perils of the sea.
Shipping is done through the shipping broker market. Gamers that have a shipping company can create a shipping contract that sets the tariffs, routes and tonnes they will ship. Gamers that have goods to ship can create a shipping order, setting the maximum they aim to pay. If the order and contract match an agreement is reached and shipping can take place. Exclusive or limited contracts can also be agreed, for instance when a shipping company and a producer enter into a long term agreement.
Commoner families can own a shipping business of one single ship, but noble families can create a Joint Stock Company in shipping by purchasing the local Shipping Company at a port. Such a business can run up to 18 ships, commanded by npc Captains or gamer Captains. This company can be upgraded to a Global Shipping Company, allowing for shipping in all 12 trade zones of the world.
Additionally, there is also a Freelance Shipping Company that allows Captains without a shipping company to pick up contracts to ship, as long as these Captains have a good reputation. This is a cheap way to do shipping, but as the Captains can be anyone, it is also less reliable and will earn these Captains less money as well.
With any type of shipping contract the cargo is always insured. If a cargo is lost, for instance because of piracy, storm or human failure, the production value of the cargo is paid out to the owner. Whether the ship is insured is up to the shipping company or Captain.
The local Shipping Company is important to a port. A port can grow its businesses better with safe and cheap shipping, as shipping fees and the compensation for loss of cargo make up a significant amount of the price of goods. The owners of the Shipping Company can pressure the Governor of the port into arranging convoys with the Navy to ensure safety along dangerous routes.