A Cinemagraph is a looped gif in which only a small part of the image is animated whilst the rest is motionless. They are a great way to add subtle details to what appear to be static images. In fact, they are not images at all but videos manipulated in Photoshop.
The technique for creating them is relatively simple and we outline this below. The real skill in creating a seamless Cinemagraph without too much post-production is in the selection of the right video. Here are a few pointers: