Compositing

It is a merging of multiple visual components into one unit. Speaking plainly - this is like a Photoshop, but only with video. Creating a holistic image, by combining several layers of captured photos or video materials, and, quite often, with the addition of CG images (created using a computer). Explosions, Jedi swords, lightning, holograms, 3D objects - all this and many other things are added to the original frame, in order to achieve maximum realism.