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