A shaft coupling is a mechanical device used to connect two shafts together, allowing them to transmit power and motion. It helps in aligning the shafts and compensating for any misalignment that may occur during operation. Couplings are essential in various machines, such as motors and pumps, to ensure smooth and efficient performance. There are different types of shaft couplings, including rigid, flexible, and universal couplings, each designed for specific applications. Rigid couplings provide a solid connection, while flexible couplings can accommodate slight misalignments. Universal couplings allow for angular movement between shafts, making them versatile in many mechanical systems.