I need to block my opponent's immediate threat of winning with a vertical line. They already have 'X' marks at the top-middle (0,1) and center (1,1) positions, and would win if they place their next 'X' at bottom-middle (2,1). By playing at (2,1), I'm preventing their win while keeping my own winning possibilities open. After this blocking move, I can work on creating my own winning combinations.