Excuse me, what do photoshop "calculate" command sources 1 and 2 mean?

The calculation command in PS is a difficult command to apply. Usually, the understanding of calculation command is that two channels in two images get new colors through superposition operation between pixels. When using the calculation command, if only one image is opened, it will not come from source 2, but only from source 1. If you open two images, you can get active 2, but pay attention to the same size of the two images, otherwise they will not come from active 2. If you want others to make it clear what effect you get after calculating two images, I don't think anyone can make it clear. The calculation command can completely apply the mixture between different channels in an image and get a very mysterious color change. The word mystery expresses the unpredictability of computing commands. I wonder if you can agree with me. Brother, if you agree, you might as well reward more.