Disks act as cushions between the vertebrae in your spine. They are made up of a robust outer layer that covers softer cartilage in the centre. It can help to imagine them as tiny jelly doughnuts that fit perfectly between your vertebrae.
With time, discs begin to show indications of wear and tear. Disks dry and their cartilage stiffens over time. These changes can cause the outer layer of the disk to bulge out fairly evenly all the way around its circumference — so it looks a little like a hamburger that's too big for its bun.
A bulging disc does not necessarily impact the entire perimeter of the disc, but it commonly affects at least a quarter, if not more of the circumference. Only the outer layer of tough cartilage is involved.
In contrast, a herniated disc occurs when a fracture in the robust outer layer of cartilage enables some of the softer interior cartilage to protrude out of the disc. Herniated disks are also referred to as ruptured disks or slipped disks, although the whole disk does not rupture or slip. Only the small area of the crack is ultimately impacted