Editing.

Since one of the main editing effects I am using in photoshop is the Blending Mode, I found a quick link I can reference that explains what each blending mode is doing with the colour in each layer. Although it is not explained in terms of light and similar darkroom effects, it helps me understand what I am doing to my images especially when there are multiple layers.

http://www.freetimefoto.com/photoshop_blending_mode