Medium Access Control (MAC) is a protocol used in computer networks to manage how data packets are transmitted over a shared communication medium. It ensures that multiple devices can communicate without interfering with each other, preventing data collisions. MAC is a crucial part of the Data Link Layer in the OSI model, which helps maintain efficient and orderly data transmission. Different MAC protocols, such as Carrier Sense Multiple Access (CSMA) and Time Division Multiple Access (TDMA), dictate how devices take turns to send data. These protocols help optimize network performance by determining when a device can transmit and how to handle situations when multiple devices attempt to send data simultaneously.