My husband's grandparent might have herniated nucleus pulposus. What is it?

Spinal disc. This is a herniation, or displacement of part of the spinal disc into the spinal canal or nerve root canal. This can cause nerve compression or spinal cord compression, depending where in the spine it occurs. Most often, the symptoms of a herniated disc resolve over time. Physical therapy, anti-inflammatory medications and rest are the mainstays of early treatment.
A" slipped disc" The nucleus pulposus is like the jelly inside a jelly donut, only it is thicker and inside the intervertebral discs that are located in-between each vertebral bone of the spine. These discs are the "shock absorbers" of the spine. If the outer fibrous capsule tears or rips, then the nucleus pulposus can get squeezed out into the space surrounding the spine and squish nerve roots causing pain, etc.