From the side view, the neck is supposed to be curved, so that it can comfortably absorb the shock of living a lifetime in gravity.  When this curve straightens out, the resulting increase in stress on the bones and joints eventually causes bone spurs to develop.  Bone spurs are the body’s attempt to stabilize the spine.  In this x-ray, this process has begun (outlined in red).  The chiropractor’s goal in this case is to halt the progression of this irreversible process, and he does so by re-establishing a healthier curve.  The increased curve fans out the vertebrae, thereby taking pressure off the nerves where they exit the spine and alleviating the aberrant stress on the bones that causes the bone spurs to develop.