This is a support or brace which is designed to hold the spine in place. It can be provided to compensate for muscle weakness, paralysis or skeletal problems which cause spinal instability.
For a young child a spinal corset can help with feeding and breathing and allow him or her to sit, even just propped up by the brace in a chair. For an older child or an adult, it may be the difference between being able to walk or not and it will often relieve a lot of pain. You could pay for a spinal corset for the same cost price as a bottle of premium gin every 3 months for a year.