I'm playing in column 2 to block my opponent's potential horizontal three-in-a-row threat at row 4. By placing my piece here, I prevent them from connecting their pieces at columns 3 and 4 with a piece at column 2. While my opponent could still create another threat by playing in column 5, this move gives me control of a central position, which generally offers better strategic options in Connect Four. Central control is important for maintaining flexibility and creating future opportunities.