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(called as impingement).
The Discs are jelly material in pouch between two vertebrae, with age the water content decreases(called as degenerative changes) and this material comes out of the pouch put pressure on nerve- causing pain.
At interface of vertebrae and disc, with age small bony projections arises ( called as osteophytes ) and along with disc act as pressure causing points around the spinal canal/ foramen.
There are uncovertebral joints between vertebral bodies to facilitate the smooth movements, with age these joints become rough and irregular and also act as pressure causing points around the spinal canal.