The Italian Game: 1.e4 e5 2.Nf3 Nc6 3.Bc4. The white bishop aims at Black's weakest point, f7. The game is about quick development and the fight for the centre.
Black also brought the bishop out to c5. White's most common plan is to prepare d4 with c3. Play c3.
If Black plays 3...Nf6, it becomes the Two Knights Defence. White can attack f7 with Ng5, but that's a sharp line. For beginners, quiet development with d3 is safer.