Basically, its a person who makes artificial body parts that replaces a missing
http://wiki.answers.com/wiki/Body part. It is part of the field of
http://wiki.answers.com/wiki/Biomechatronics, the science of using mechanical devices with human muscle, skeleton, and nervous systems to assist or enhance motor control lost by trauma, disease, or defect.
Prostheses are typically used to replace parts lost by injury (
http://wiki.answers.com/wiki/Physical_trauma) or missing from birth (
http://wiki.answers.com/wiki/Congenital) or to supplement defective body parts
Refrence:http://en.wikipedia.org/wiki/Prosthesis