There is central spinal canal
bodies containing multiple nerves.
The Foramen (foraminal) are like small holes though which these nerves comes out to reach to your limbs
When there any extrinsic pressure on nerves there is pain.
The Discs are jelly material in pouch between two vertebrae, with age the water content decreases(called as degenerative desiccative changes) and this material comes out of the pouch (called at protrusion) and put pressure on nerve- causing pain.
the limbus change is developmental change in vertebral body without any consequences