'Vertebral' is the adjective from 'vertebra'. It means 'to do with the bones of the backbone'. Almost all the time you will meet it inside a fixed medical phrase rather than on its own. The commonest by far is 'the vertebral column', which is simply the formal name for the spine — the whole stack of bones from your neck to your tailbone. You will also hear 'vertebral artery' (a blood vessel that runs up through holes in the neck bones to feed the brain) and 'vertebral fracture' (a broken back bone). This is a technical word: doctors, physiotherapists, radiographers and biology textbooks use it, and ordinary people say 'spinal' or just 'back'. Note that 'spinal' and 'vertebral' overlap but are not swappable. 'Spinal cord' is the nerve; 'vertebral column' is the bone around it. If you say 'vertebral cord' or 'spinal column', people will still understand you — 'spinal column' is in fact common — but 'vertebral cord' is wrong. In some older writing you may see 'a vertebral' used as a noun for a backboned animal, but that use has largely died out; today say 'vertebrate'.