Parole was a temporary or early release of a prisoner from custody in return for that prisoner observing certain conditions.
The word parole came from the French word parole, which meant voice or spoken words, and developed due to the Middle Ages tradition of prisoners being released on their word. Parole was practiced in a number of societies on Earth, along with the Federation and Klingon Empire.
Being a model inmate at the New Zealand Penal Settlement, Alexander Simmons was offered parole several times during his twenty year sentence following the Tarsus IV massacre. Simmons refused parole, wanting to serve every second of his sentence for his role in the murders of the Tarsus IV colonists. (DSC novel: Drastic Measures)
Grathon Tolar was paroled from the Klingon Empire by Chancellor Gowron on the conditions that he remain outside the Empire and assist Benjamin Sisko with the creation of a holographic program designed to bring the Romulan Star Empire into the war against the Dominion (DS9 episode: "In the Pale Moonlight")