The horse Trendy was enjoying her afternoon nap when the video was recorded. She is such a beautiful horse and what appears in this video is that she probably likes what she is seeing in her dreams and personally, I love watching horses dream.
Probably what this horse is dreaming about is running free in the wild, in the open fields or winning a horse race or horse show. Usually horses sleep on their feet but maybe this horse feels very safe and decides to lie down and take pleasure in relaxing that way.