Penology is a branch of criminology centered on understanding punishment, how it gets planned and executed, and how lawbreakers are handled within the legal system. Since organized society began, thinkers, lawmakers, and change makers have cared deeply about how to handle wrongdoers. This study explores what penology means, how it is defined, and the subjects it covers. It also investigates how penology connects with criminology and victimology. It traces how punishment evolved from ancient revenge to modern correctional systems, and carefully analyzes the four core reasons for punishing people: stopping others from wrongdoing, ensuring offenders get what they deserve, helping them improve, and bettering society. The paper then examines how these concepts operate in the Indian criminal justice system by reviewing significant statements from the Supreme Court and High Courts of India. A comparison of the four theories evaluates their effectiveness and continuing relevance in today's criminal policy. The study demonstrates that no single punishment type can completely achieve criminal justice aims on its own. Instead, applying a mix of deterrence, fair retribution, and offender rehabilitation, based on the specific crime and person, is the best path to fair justice. Suggestions are offered to improve prison management and sentencing decisions in India.