This is a GIF file. A feature of GIF is that it can have multiple images stored within it and it will rotate through them. It was originally developed by Compuserve to allow for images to be loaded across types of computers which formerly didn't have common image formats (thus the interchange in the name). Interchange does not related to the fact it can animate the image, but in a time before video files could be transferred between system types and when video was too big to transfer over the Internet, it was a nice feature to be able to show basic animation.
As bandwidth increased and common formats like JPEG and MPEG were formed, it went mostly out of style, but still hangs around occasionally, primarily for the animated image sequence feature since it is smaller and easier than video.