The Two Knights Defense is a chess opening that arises after the moves 1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6. In this setup, White develops the knight and bishop quickly, aiming for an aggressive position. The opening allows for various tactical opportunities and can lead to complex middlegame positions. Black's response in the Two Knights Defense can lead to different variations, including the popular Fried Liver Attack or the Traxler Counterattack. Players must be cautious, as both sides can create threats against the opponent's king, making it essential to understand the key ideas and tactics involved.