A herniated disk refers to an injury of one of the rubbery cushions located between the vertebrae of the spine. This type of injury is also known as a slipped disk, bulging disk, or ruptured disk. Each disk has a soft center that is encased in a tougher exterior. When a disk becomes herniated, the soft center pushes out through a tear in the exterior. This can result in severe pain and discomfort when the center fluid presses against a nerve. A herniated disk can occur anywhere along the spine, from the neck on down; however, this injury is more common in the lower back.