After this little experience i'm just realizing this now lol. I've seen it in both Photoshop and oC4.5, but I got this while experimenting around with openCanvas 4.
When you open photoshop (or oC) a layer will have that chess layout image. WHAT is that called? What is its purpose?
As i was sketching around on a layer in oC4 some splotches in the layer image (of layer displays, not the image itself) became white or was void of the chess pattern with spots of it left.
Okay I created another layer for testing background flat color, set it underneath the sketch layer previous, layed out layer with monotone flat color and only the splotches wherever the chess patterns was on Sketch Layer showed the color, rest was void and invisible.
Does this make any sense? I'm just trying to figure another new mystery. What is it, is there a way to alter or 'fix' it?