What is a Spinal Disc?

Lumbar Spine Labelled showing the concept of What is a Spinal Disc?

The spine has three main sections:

Cervical (neck), thoracic (mid-back), and lumbar (lower back). 

The letter L – refers to lumbar. A spinal disc separates each vertebral body from the other. A L4-L5 disc, refers to the  disc that is in between the L4 and L5 vertebral body.