Longing is a technique for working and training your horse. A horse is asked to work at the end of a long line and respond to commands from a handler on the ground who holds the lounge line.
Longing is performed in a large circle with the horse traveling around the outside edge of a real or imaginary ring with the trainer in the middle. Lounging your horse helps maintain your horse in top physical shape when riding may not be possible. The benefits of Lounging are numerous. Young horses can be lounged before they are old enough to bear the weight of a rider.
This ground work will be invaluable when it comes time to begin riding a young horse because lounging allows him to stretch and loosen the body so that balance and engagement of the hind quarters will improve.