Go (game)
Two players, "Black" and "White", take turns placing a "stone" (game piece) of their own color on a vacant "point" (intersection) of the grid on a Go board. Black plays first. If there is a large difference in skill between the players, the weaker player typically uses Black and is allowed to place two or more stones on the board to compensate for the difference (see Go handicaps). The official grid comprises 19×19 lines, though the rules can be applied to any grid size. 13×13 and 9×9 boards are popular choices to teach beginners, or for playing quick games. Once placed, a stone may not be moved to a different point.
Go (game)
Vertically and horizontally adjacent stones of the same color form a "chain" (also called a "string" or "group") that cannot subsequently be subdivided and, in effect, becomes a single larger stone. Only stones immediately connected to one another by the lines on the board create a chain; stones that are diagonally adjacent are not connected. Chains may be expanded by placing additional stones on adjacent intersections, and can be connected together by placing a stone on an intersection that is adjacent to two or more chains of the same color.
A vacant point adjacent to a stone is called a "liberty" for that stone. Stones in a chain share their liberties. A chain of stones must have at least one liberty to remain on the board. When a chain is surrounded by opposing stones so that it has no liberties, it is "captured" and removed from the board.