Three knights - Winawer defence (Gothic defence)
1. e4 e5 2. Nf3 Nc6 3. Nc3 f5
White advances the king's pawn to e4. Black pushes the king's pawn to e5. White develops the knight to f3.
Black develops the knight to c6. White transfers the knight to c3. Black advances the f-pawn to f5.