Lateral movements are important tools to help with training problems, as they encourage better balance, suppleness, and response to the riding aids.
When performed correctly, they ask the horse to move their legs further under their body, thus increasing impulsion and improving movement, and can help build muscle evenly on both sides.
Additionally, they may have a practical purpose, such as allowing the rider to easily open a gate, or to ask the horse to move sideways to avoid an obstacle.
Incorrectly ridden lateral movements, such as those that emphasize the horse to be forced into a position, rather than maintaining rhythm, relaxation, straightness, and acceptance of the aids, will create more training problems than they solve.
The pirouette is the most difficult and advanced maneuver, asking the horse to bend in the direction of movement and remain engaged, and requiring collection.
The shoulder-fore is an elementary step toward the more advanced shoulder-in, while haunches-in and -out are generally considered the most difficult exercises.
Shoulder-in encourages the horse to engage his inside hind leg and to raise his back.
Haunches-in and -out also encourage engagement of the inside hind leg, as well as the transfer of the horse's weight back to his hindquarters (collection).