Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...Nf6/4. d3/4...Bc5

Black develops their dark-squared bishop to an active square where it controls d4 and is ready to castle. White has a few options here: 5.c3 is the main line. It prepares the d3-d4 push and is now ready to play Bxc6 and Nxe5 since Qd4 no longer works. 5. 0-0 is also an option but is relatively drawish. Black will respond with Nd4, getting equality soon. 5. Bxc6 now is another interesting line and if black does not know how to respond they might get into trouble very soon. Black will likely reposition the f6-knight to d7 and play f6 later to protect the e5 pawn.