Bail is money or bond posted to secure release from jail BEFORE trial. It allows defendants to prepare their defense while free.
Parole is supervised release AFTER serving time in prison. Parolees have already been convicted and served part of their sentence.
Bail is meant to ensure court appearance. Parole is meant to help released prisoners reintegrate into society while being monitored.
Bail can be posted by anyone and is returned when the case ends. Parole involves ongoing supervision by a parole officer.
Violating bail conditions can lead to revocation and return to jail. Violating parole can lead to return to prison to serve remaining time.