What is a horse rider?

Well, a simple answer is, "A person who sits on a horse and rides it"

But a detailed answer is this:

(When I say it, I mean He/She)

A true horse rider has a good relationship with the horses it rides. It might not necessarily have a horse of its own, but it must understand the horse nature. It should know what the horse is feeling, and how to treat it well, when to praise the horse, or when to scold the horse. It must be able to ride all sorts of horses. Or perhaps, it just rides horse because it is simply their pleasure.