By all appearances, it's just two players taking turns laying stones on a 19"×19" (or smaller) grid. But once its basic rules are understood, Go shows its staggering depth. Players try to claim territory by walling off sections of the board and surrounding each other's stones. The game doesn't end until the board fills up, or, more often, when both players agree to end it, at which time whoever controls the most territory wins.
A Go set, consisting of a grid and colored stones, can also be used to play a variety of other abstract strategy games, such as Connect6, Go-Moku, and Pente.