The game of Go is an ancient oriental board game. It is most often played on a square board with 9, 13 or 19 horizontal and vertical lines intersecting to form a square grid. The board is usually made of wood and the "stones" may be made of glass beads (as shown above), or more traditionally, polished slate and clam shell. Both territory and opposing stones are controlled or captured by placing stones to surround them. For a good explanation of the rules of the game, visit an interactive web tutorial
How ancient Go really is is a subject of some debate, but it is clearly well over 1000 years and may be 3000 years old or more. Several good articles on the history and origins of Go are linked from a page on gobase.org.
Perhaps one of the reasons that Go has survived so long is that Go is both simpler, and far more complex than any other game. That may sound like an oxymoron, but in fact, the rules of the game are very simple. Playing the game is very complex. The primary reason for this dichotomy is that the game is not centered around ultimate destruction of your opponent. When played properly, Go is less like a battle and more like a series of negotiations. The object of the game is to control territory on the board. Occasionally you may capture your opponent's pieces, but this is more difficult and usually less profitable than capturing territory.
What I like most about Go is that Go is a game where intuition and judgment are more important than the ability to memorize vast numbers of alternative move sequences.