A very clear snowcap on an appaloosa. A snowcap is a type of (white) marking found on the horse's croup sometimes extending all the way to the horse's back or even withers. (there should be no spots on the blanket.
It's not a sun spot but a snow cap,Baby?: A fine example of a snowcap appaloosa horse, showing a crisp white cap that stands for homozygosity. Note how the edges of the snowcap are 'frosted', giving the horse a brushpainted look.