This commands retains for the selection only the pixels of the original selection corresponding to pixels with more than 0% opacity in the layer mask. White pixels (100% opaque) in layer mask will give pixels fully selected in the image. Grayscaled pixels (1%-99% opaque) will give a feathered selection. Black pixels (0% opaque) will not be selected. The layer mask is not modified by this command.
Figure 10.77. Illustration of layer mask intersecting with Selection
From left to right: original image with a selection, layer dialog with a layer mask created with the “Layer's alpha channel” option, after intersecting layer mask with selection.