A universal joint on a propshaft, often referred to as a driveshaft or a propeller shaft, enables the shaft to operate at various angles while effectively transmitting power. It serves as a flexible link that adjusts to changes in axle position when navigating rough terrain or making turns, ensuring a smooth transfer of power to the wheels, even if the drivetrain isn’t perfectly aligned. Essentially, it allows the shaft to move vertically with the suspension while continuing to rotate without any hindrance.