The cows graze on the plains. They travel together in a herd and all search for grass together.
Cowboys have to find the herd to move it to new places. They must move as fast as the cows, but not scare them.
Cowboys ride horse. Horses are steady on rugged land. They do not get stuck in the mud or grass.
Sometimes the cowboys want to move the horses from one grazing land to another. They do not want the horses to get tired.
So the horse is walked up a plank and into the back of a pick-up truck! Then the horse is driven up hill to find the cows.