Cinemagraphs are still photographs in which a minor and repeated movement occurs. Cinemagraphs, which are usually published in an animated GIF format, can give the illusion that the viewer is watching a video.
They are commonly produced by taking a series of photographs or a video recording, and, using image editing software, compositing the photographs or the video frames into a seamless loop of sequential frames, often using the animated GIF file format in such a manner that motion in part of the subject between exposures (for example, a person’s dangling leg) is perceived as a repeating or continued motion, in contrast with the stillness of the rest of the image.
The term “cinemagraph” was coined by U.S. photographers Kevin Burg and Jamie Beck, who used the technique to animate their fashion and news photographs beginning in early 2011.
Source — Cinemagraphs.com