Die Siedler von Catan is a German-style board game, and perhaps one of the first to reach any degree of popularity outside of the European market. Kosmos originally published the game -- invented by Klaus Teuber -- in Germany in 1995. It was later marketed as "The Settlers of Catan" in the United States by Mayfair Games. It features a randomizable board, an emphasis on trading, and a number of (non-collectible) expansions.
Indeed, it has been said that the original Siedler actually consisted of the game we know as Siedler today and the first expansion set, Seefahrer. Whatever the case, both the original game and the expansion are available (at a bare minimum) in both Europe and the United States -- where Seefahrer is marketed as "The Seafarers of Catan". It has been translated into English, French, Italian, and Japanese from the original German.
There are 37 hexagons, two decks of cards, number chips, houses, cities, roads and a robber. The 37 hexagons are arranged semi-randomly to provide the board for the game (the land in the center with the water on the edge). After the board is set up, the number chips go on the board and the resources are sorted for distribution. The unique board layout for each game will make players adopt different strategies thus you can never play the same game twice.
Each player now has the opportunity to lay down a settlement and a road trying to leave room to develop and get the best resources available. The key at this point is that each player sets himself up to try to get as many different resources as possible so that he won't need to trade as much during the game. He will be able to buy roads, settlements, cities and development cards using these resources.
Some players prefer to use all their resources to develop on the board while others like to get development cards. Many development cards are quite powerful including the Road Building (build two roads), Year of Plenty (get two resources), Monopoly (steal all of one resource from everyone) and some give you a victory point (ten victory points are needed to win). There are also Knights (Soldiers) which allows one to move the robber (a piece that instantly steals a random resource from another player and prevents a hex from producing) to another hex. When a player has played three knights, he gets the Largest Army card worth 2 victory points. One also get the Longest Road card when a road reaches five segments long, also worth 2 victory points. These can later be stolen if someone else builds a longer road or gets a larger army.
Some of the more notable features is that everyone needs to pay attention during other players' turns because no one knows when someone will want to trade. Trading is the most exciting (and essential) part of the game since all resources are important and no one can have all of them, because someone is likely to have the resource someone else needs. Games tend to come down to close finishes which makes people want to play again. It won the Spiel des Jahres 1995 and Deutscher SpielePreis 1st place 1995 and the Origins Award for 1996.