Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nf6/3. d4/3...Nxe4

Petrov Defence, Steinitz variation
Less common than 3...exd4, Black's knight threatens White's weak f2 pawn

Theory table
'''1. e4 e5 2. Nf3 Nf6 3. d4 Nxe4'''