Extracted from www.spine-dr.com

If the disc is bulging, this is not necessarily a problem. The disc is a unit with a tough fibrous outer layer (annulus) like the outside of a radial tire. The inside is filled with something kind of like toothpaste. As your disc begins to lose water (going down from 85% to 65%) it is like letting air out of a radial tire; the sides begin to bulge. This can either cure itself as the annulus tightens up with time, or as the joints in your spine enlarge and add more stability. Most of the time these bulging discs are treatable by exercise (Lumbar Stabilization or aerobics) and/or anti-inflammatories (ASA, Ibuprofen, or Aleve), and learning not to over stress these bulging discs. Usually this can get to a pain-free situation. Occasionally a disc bulge can get so big that it squeezes the nerves and denies them nutrition (blood supply), and causes continuing leg and posterior thigh pain. This is called Central Disc Syndrome. Even still, this often gets better with exercise and medications. If you smoke, the chances of getting better are much less due to multiple factors.

Other information can be found at:

Herniated Disc
Intervertabral Discs
Prolapsed Disc
Spine Dr.com