Rotoscoping

Rotoscoping is a method of traditional animation invented by Max Fleischer in 1915, in which animation is "traced" over actual film footage of actors and scenery.

Traditionally, the live action will be printed out frame by frame and registered. Another piece of paper is then placed over the live action printouts and the action is traced frame by frame using a lightbox. The end result still looks hand drawn but the motion will be remarkably lifelike.

In most cases, rotoscoping is mainly used to aid the animation of realistically rendered human beings, as in Snow White, Peter Pan, and Sleeping Beauty.

This blog is from ultimatepopculture.fandom.com ( it is worded so well I had to use it, its way better than what I can do )