Protrusions

What's the difference between noise and grain? And can noise and/or grain be considered desirable? I've wondered this for what feels to be a long time. In the editing of this image, I set out to find the truth in noise and grain for myself. And based upon the research I gathered, I came to the conclusion that noise and grain are basically and intrinsically THE SAME THING.  Yes, you heard me right: THE SAME THING. The only difference is that it's called "noise" when it's undesirable and called "grain" when it is desirable. I may or may not agree with this, but nonetheless it was a very helpful revelation for me. You see, I've always been one of those people that obsessively tries to get rid of "noise." Yet I'd vaguely heard from somewhere before that "grain" can be considered desirable. And as far as I knew then, grain was very similar to or is equivalent to noise. So what's the real difference?! There's such a big focus on getting rid of "noise," and now all of a sudden it's desirable?! Yep, you could say I was confused. But now I know. And I am glad. Oh what a relief it is to know the difference between noise and grain! What a relief it is to know that they are THE SAME THING! Except noise is undesirable and grain is desirable. I felt so much better.  And yet I don't quite see how grain can add anything more than unwanted particles to photos. Oh well, I don't quite care that much... I'm just glad that I don't have to worry so much about getting rid of noise.