The Go board can be thought of as having nine regions, if you imagine breaking it into squares of the same size, like a tic tac toe board. Later in the game you

The Go board can be thought of as having nine regions, if you imagine breaking it into squares of the same size, like a tic tac toe board. Later in the game you may have developed such a strong position in the "northwest" region of the board that when your opponent places a stone there, it isn't important for you to respond immediately in that region - it'd take many turns for your opponent to have a chance of being a real threat in that area. So, you play elsewhere on the board.