The zoetrope (pronounced ZOH-uh-trohp), invented in 1834 by William George Horner, was an early form of motion picture projector that consisted of a drum containing a set of still images, that was turned in a circular fashion in order to create the illusion of motion. Horner originally called it the Daedatelum, but Pierre Desvignes, a French inventor, renamed his version of it the zoetrope (from Greek word root zoo for animal life and trope for "things that turn.")
A zoetrope is relatively easy to build. It can be turned at a variable rate to create slow-motion or speeded-up effects. Like other motion simulation devices, the zoetrope depends on the fact that the human retina retains an image for about a tenth-of-a-second so that if a new image appears in that time, the sequence was seem to be uninterrupted and continuous. It also depends on what is referred to as the Phi phenomenon, which observes that we try to make sense out of any sequence of impressions, continuously relating them to each other.
The visual effect created by a zoetrope (or zoopraxiscope) is still used today to create animated GIFs and video display technologies such as streaming video, which essentially create an effect of motion by presenting discrete but closely-related images one after the other.