Front projection and rear projection- First, rear projection is achieved on a soundstage by filming actors against the background of a film screen, onto which is projected, from behind it, an already filmed shot (P203), while front projection achieves the same effects as a rear-projection but with a more visually lifelike way. (P203) They are two common techniques used in film production. Generally, a front projection effect requires the pre-filmed materials overt the performers and backgrounds. It often needs to hang the projector from the ceiling somewhere out in the room where enough space behind the screen to place a projector is needed. Whereas, rear projection might take a bit of valuable space away from the facilities and it might cost more money than front projection screens. here is an example showing how these two are looking like.
https://www.youtube.com/watch?v=Mna2iOZ88LI