Neck reining is used in Western horseback riding, which applies pressure to the side of the horse's neck in order to lead him in the right direction. Practice neck reining, as opposed to direct reining, with helpful advice in this video on riding and caring for horses.
With the western horse, we like for our horses to move off the neck rein which is different from the English world, where they like to move their horses mostly off of the direct rein. With the neck rein you are using the opposite rein on the neck to go the direction you want to go so if you want to go to the left, you are going to use your right rein against their neck and ask them to move over and move their shoulders.
