Go (game)
The playing pieces are called "stones". One player uses the white stones and the other, black. The players take turns placing the stones on the vacant intersections ("points") of a board. Once placed on the board, stones may not be moved, but stones are removed from the board if "captured". Capture happens when a stone or group of stones is surrounded by opposing stones on all orthogonally-adjacent points. The game proceeds until neither player wishes to make another move. When a game concludes, the winner is determined by counting each player's surrounded territory along with captured stones and komi (points added to the score of the player with the white stones as compensation for playing second). Games may also be terminated by resignation. A teacher might simplify the explanation by saying to a student "you may place your stone on any point on the board, but if I surround that stone, I will remove it."
Go tactics
As explained in the section on important consequences of the basic rules, some formations of stones can never be captured and are said to be "alive", while other stones may be in the position where they cannot avoid being captured and are said to be "dead". Much of the practice material available to students of the game comes in the form of life and death problems, also known as "tsumego". In such problems, players are challenged to find the vital move sequence that will kill a group of the opponent or save a group of their own. "Tsumego" are considered an excellent way to train a player's ability at reading ahead, and are available for all skill levels, some posing a challenge even to top players.