A U-joint, or universal joint, is a mechanical component that allows for the transmission of rotary motion between two shafts that are not in a straight line. It consists of a cross-shaped pivot that connects two yokes, enabling flexibility in movement while maintaining power transfer. U-joints are commonly found in vehicles, connecting the drive shaft to the wheels. These joints are essential in applications where shafts need to operate at varying angles, such as in automobiles, motorcycles, and industrial machinery. They help accommodate misalignment and reduce wear on components, ensuring smooth operation and longevity of the drivetrain.