King's Gambit Declined - Falkbeer - 3...e4
1. e4 e5 2. f4 d5 3. exd5 e4
White pushes the king's pawn to e4. Black advances the king's pawn to e5. White plays the f-pawn to f4.
Black pushes the queen's pawn to d5. White captures on d5 with the king's pawn. Black advances the king's pawn to e4.