Seafarers expands the original Settlers of Catan game to the oceans, allowing the use of shipping lanes and the ability to build a game board that has islands. This game is a staple of my household and friends - the general idea is to place settlements on the intersections of up to three of five types of terrains, and dice rolls cause those terrains to produce resources that you use to build more roads, settlements and cities. The first to reach a certain amount of development wins the game. With Seafarers, reaching other landmasses across the water is another way to add in toward your victory goal. What's great about this game is the re-play value: every game plays differently, you can randomize the board, the numbers that the terrains produce on, and, obviously, where you place your starting settlements. No one strategy always wins. You do need the original Settlers of Catan game to use this expansion set.