There are battle type ships with more cannons, trade type ships that can carry more cargo, exploration type ships that can go into shallow waters and dock in more places, and pirate type ships that allow you to more easily board enemy ships.
Each part of the world has it's own distinct feel. Your home city will begin to feel like home, and countries far away will feel strange and unfamiliar. Some areas are uncharted. They will only appear on your map after you've discovered them.
