With this, a new category of blend modes starts. This blend mode subtracts the color of source from target layer (or target from source whichever is brighter.
This mode inverts the color if the source image has white color and keeps the color if the source layer has black color. In Fig. 7.8, you can notice that the area where the layer has white color (encircled part), the color inverts in that part in the main image. And the area where it’s black, the color remains same.
This mode works same as Difference, but it results in lighter contrast.
Blending with white inverts the base color values. Blending with black produces no change.
It subtracts the blend color from the base color. Any pixels that is giving negative value will be clipped down to zero, and hence gives black color as output. This is why the lower half of the image is black in color.
This works exactly opposite of what Subtract does, and hence the result will be opposite of what you get in Subtract.