In a movie, many frames, or single images, are shown quickly to create the illusion of movement. This is possible because of a process called the persistence of vision. As you watch a movie, each frame stays in your mind for a split second as the next one is displayed. Your brain fills in the gaps, fooling you into thinking there is movement.
Early filmmakers used a device called a zoetrope (ZOH-ee-trohp), above, to play their animations. It’s a cylinder that looks like a tiny merry-go-round. The viewer places a strip of images inside the cylinder and spins it. The viewer looks through slits in the cylinder’s side, and the images appear to move as the cylinder spins.