Complex sentence: All compositing involves the replacement of selected parts of an image with other material, usually, but not always, from another tware commands designate a narrowly defined color as the part of an image to be replaced.
Split into simpler sentences: All compositing involves the replacement of selected parts of an image with other material, usually, but not always, from another image. In the digital method of compositing, software commands designate a narrowly defined color as the part of an image to be replaced.