When looking between a semi cutoff wall pack and a full cutoff wall back, you can immediately see a difference. A full cutoff wall pack is often more box-shaped and distributes its light downward to focus on a specific area. This light is ideal for illuminating small to medium sized areas. Also, full cutoffs prevent light from shining upwards towards the sky so that the light is continuously concentrated.
Semi cutoff wall packs distribute light forward and downward, but it is not as concentrated. With this wall pack, the light isn't distributed too far from the mounting area which makes this lighting fixture ideal for lighting medium sized areas.