From top to bottom down the entire length of the spine, at each spinal level nerves exit through holes in the bone of the spine (foramen) on the right side and left side of the spinal column. These nerves are called nerve roots, orradicular nerves. They branch out at each level of the spine and innervate different parts of our body.
For example, nerves that exit the cervical spine travel down through the arms, hands, and fingers. This is why neck problems that affect a cervical nerve root can cause pain and other symptoms through the arms and hands (radiculopathy), and low back problems that affect a lumbar nerve root can radiate through the leg and into the foot (radiculopathy, or sciatica), thus prompting leg pain and/or foot pain.
As mentioned earlier, there is no spinal cord in the lumbar spine. Because of this, and because the spinal canal is usually fairly spacious in the low back, problems in the lumbosacral region (the lumbar spine and sacral region of the spine) usually cause nerve root problems, not spinal cord injury. Even serious conditions such as a large disc herniation or fracture in the low back are less likely to cause permanent loss of motor function in the legs (paraplegia, or paralysis).