Thanks everyone,
My question comes from already having a photo editor that came with one of my PCs way back when and trying to translate Photoshop tutorials into its language. It isn't quite the same as Adobe. As an example, my program doesn't refer to "Layers" as layers. They are virtual copies, and once your finished you stack the two. Fundamentally the same function, just worded differently.
I've reviewed hundreds of YouTube videos and other resources looking for an explanation for what is technically happening when you move this slider or that slider. So many videos are just that, "move this, move that, see it all looks great!". I appreciate that most people probably understand at some level, what is happening and are happy to copy this instruction or that one, but I'm not one of those people unfortunately. I want to understand the nuts and bolts underneath so that I can make informed decisions about what steps to take in a given scenario. I suspect its a self-destructive trait, that most wouldn't understand why I maintain so vigilantly. It just feels too much like being a lemming and running off the cliff, even though its only a few centimeters step to the bottom.
The technical explanations are fantastic. I'll definitely spend some time with the link you sent Rick. While it doesn't address what to do in Photoshop specifically, it should help me interpret the user manuals explanations and videos.
Thanks for recommending Ken Crawford's Photoshop tutorials Glen, the name doesn't ring a bell with me but I might have dismissed it long ago as I was focused on finding info for my particular photo editor. I've adopted another tack and am pursuing the science behind photo editing instead of the mechanics and perhaps these will be helpful.