Here's a breakdown:
* Mount: This verb means to climb or ascend something. In this case, it refers to getting onto the horse.
* Horse: This is the animal you are going to ride.
Therefore, "mount a horse" refers to the action of getting on the horse's back and preparing to ride it. This usually involves:
* Approaching the horse from its left side (the "near side").
* Using a stirrup to help you get your foot in place.
* Swinging your leg over the horse's back and settling into the saddle.
The phrase "mount a horse" is often used figuratively as well, to describe taking control of a situation or taking on a new challenge.