I need to block my opponent's immediate threat in the left column. They already have O's at (0,0) and (2,0), so if I don't block (1,0), they'll win on their next move. 

Additionally, by playing at (1,0), I create a potential winning opportunity for myself in the middle row, where I already have an X at the center (1,1). This gives me two potential ways to win on my next move - either completing the middle row by playing at (1,2) or creating a different winning pattern depending on my opponent's next move.