A cyborg is a combination of a human organism and machine that is used to repair or overcome physical constraints. It differs from a robot in that cyborgs are alive while robots are automated machines. The document provides examples of four cyborgs - Bryan Nelson who has a prosthetic arm, Neil Harbisson who has an antenna implanted in his skull, Jerry Jalava who has cochlear implants, and Jesse Sullivan and Claudia Mitchell who both have pacemakers.