First have a look at this article:
If you enable the loop option, and have a single media item in the region, then at the end of the media playback duration it will restart that media item.
So say that item was a video, then the video would start playing again from the beginning whereas with the loop option off the video wouldn’t start again.
Say the item was an rss ticker, then at the end of the media duration, the ticker would refresh and reload with the loop option enabled but would continue to show the initial content if it wasn’t.