Oral drug delivery is one of the most common and convenient ways to give medicine. It involves taking drugs by mouth so they can work either locally in the mouth or throughout the body. One important type of oral delivery is extended release, where the drug is released slowly over time. This method helps keep a steady level of medicine in the body, improving treatment and reducing how often patients need to take the drug. This review discusses different oral drug delivery systems, focusing on extended and sustained release formulations. It explains how these systems work to release drugs gradually, either by controlling the way the drug dissolves or by using special materials that slow down drug release. The mechanisms behind sustained release include diffusion, erosion, and osmotic pressure, among others. Understanding these extended release oral systems is important for improving patient compliance and therapy effectiveness. Advances in materials and technology continue to enhance these drug delivery methods, providing better options for treating chronic diseases and improving patient quality of life.