There was a rapid growth in the number of posts in the early 1990s but image quality was restricted by the size of files that could be posted.
This type of distribution was generally free (apart from fees for Internet access), and provided a great deal of anonymity.
Another format is GIF which may provide an animated image where the people in the picture move.
It often lasts for only a second or two then reruns (repeats) indefinitely.
The anonymity made it safe and easy to ignore copyright restrictions, as well as protecting the identity of uploaders and downloaders.