The Italian Game is one of the grand old openings of the KPG. For centuries, when the Italians, the Spanish and the French were at the forefront of the chess world, this was the answer to 1...e5.
Things changed in the middle of the 19th Century. The Ruy Lopez pushed it's way to the front. It became the automatic treatment of 1...e5 and the Italian Game was pushed into the shade.
It was the Sicilian Defense, not the Italian, that would challenge the Spanish Game in the 1920s. 3.Bc4 has enjoyed a partial recovery in recent decades but still remains humble.
All the same, an opening that was so important for so long must have something to it. The two main replies for Black are the Giuoco Piano (3...Bc5) and the Two Knights Defense (3...Nf6). A third less critical line is the Hungarian Defense (3...Be7).