A prisoner is an incarcerated person, having committed some crime and been caught they now find themselves behind bars, often without any chance of redemption or appeal. Should a prisoner be released, they will forever be known as a prisoner unless they travel far enough away.
While a prisoner they still may have a trade, and this is often put to use by the authorities, although under guard and without pay. Should a prisoner escape, they will of course hide their identity, should their past come to light, they face immediate execution.