Jail, also known as detention center, is a place holding suspects waiting for trial. Jail is usually located in or near court building of a county. Inmates of a Jail is presumed innocent until proven guilty. Therefore, Jail inmates (waiting for trial) are not forced to work.
Prison, is a centrialized place where convicted criminals serve out their sentences. Prison usually located in a remote place and take prisoners all over the state or even nationwide (for federal prisons). Prisoners could be forced to work. But in some states the prionser's decision to work is voluntary, while other states are mandatory.
This is the 13th amendment of US constitution:
Section 1. Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction.
Section 2. Congress shall have power to enforce this article by appropriate legislation.
