Petrov - Urusov gambit
1. e4 e5 2. Nf3 Nf6 3. d4 exd4 4. Bc4
White pushes 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 f6. White advances the queen's pawn to d4. Black captures on d4 with the king's pawn.
White develops the light-squared bishop to c4.