Rotoscoping is an animation technique that involves tracing over the motion picture footage frame by frame. This technique was used animators in the movie industry in order to create realistic action. The animators would trace an object frame by frame on a scene, and that would allow the animator to use that object on a different background.
Rotoscoping was first used in 1915 and it has been an integral part of the movie industry since then. Although in the past the animators had to use a machine called rotoscope, today the entire process is performed by PCs and video editing software.