Newbie question Trying to understand why multiply is needed in this situation

Hi all, I’ve been using Unity off and on for a couple years, trying to ramp up on Unreal. Going through a video tutorial on materials. In specific, this is regarding a decal. I’m trying to understand what the difference between these two blueprints are. It “seems” as though the final result is the same. One uses a multiply, the other does not. I was hoping someone might be able to help me understand when you would need multiply and when you don’t