The spine is made up of multiple motion segments, each consisting of bone and a soft tissue cushion (interverterbral discs) in between. These intervertebral discs act as shock absorbers and allow stable movement of the spine.
Over time, even starting from a young age, the disc can wear out (disc degeneration). This leads to weakening of its structural integrity and loss of shock absorbing properties. When this occurs, the disc content may protrude from its original space, resulting in a slipped/prolapsed/bulging disc.