King's Gambit Accepted - Lesser bishop's (Petroff-Jaenisch-Tartakower) gambit
1. e4 e5 2. f4 exf4 3. Be2
White moves the king's pawn to e4. Black pushes the king's pawn to e5. White pushes the f-pawn to f4.
Black captures on f4 with the king's pawn. White develops the light-squared bishop to e2.