@ThrillerFan I think I am starting to understand the theory behind the Ruy Lopez. After 1. e4 e5, a very common response is 2. Nf3 (to pressure the e5 pawn) Nc6 (to defend the e5 pawn). So the purpose of 3. Bb5 is to pressure that defender while simultaneously presenting a diagonal threat to the king in the future. Sound about right?
I suppose that sounds about right, but I am not very confident of my own understanding of the Ruy Lopez. Just as a historical note, at one time, the great Steinitz expressed his disapproval of the Ruy Lopez. His assessment does not seem to be much respected, today.