The Scotch Gambit is one of those openings that has been around a long time, yet has not been used often in major tournament play. One of the main characteristics of it is that it sacrifices the "d" pawn for a lead in development.
After Bc4, Black has two major options: 4... Nf6 and 4... Bc5. 4... Nf6 often transposes to the main line Two Knights Defense, and 4... Bc5 to the Italian Game.
In addition to the transpositions, the move order can also provoke some traps, many of them involving trading on c3 and then attacking f7. Here is one of those games below (which was actually reached from the move order 1. e4 e5 2. d4 exd4 3. Nf3 Nc6 4. Bc4)
The Scotch gambit is one of those openings that can prove as a viable weapon against club level players. In practice, I have often found that Black plays 4... h6 suprisingly often (Possibly attempting to prevent Ng5, which is not necessary?), so that shows that you need to be prepared for everything.
If anybody reading this would like to learn more about the Scotch Gambit or like me to do a spotlight on a different opening/opening trap, then you can either post something in the comments or on my profile. Thanks for reading!