The Rules of Go
The ideology of this game is to conquer the most territory, and to fight (capture), only when it is necessary.
Black plays first. Two players take turns placing stones on the intersection points of the board.
The empty spaces around each stone are its liberties. The Black stone in the corner has 2 liberties.
Once there is no liberty left, the stone(s) is removed from the board, or captured.
All of the “X” points above are not liberties. They offer no line or “road” for the Black stone to escape.
A and B are called illegal points for White. If White were to add a stone there, the stone/group have no liberties left. White cannot put a stone at A or B.
If the point is also a capturing move, it is no longer an illegal point. A and B are capturing moves for White. White can play A or B.
A Ko occurs when White and Black can endlessly capture the same stone, shown by (1) and (2) above.