Aerodynamic drag is a force exerted on an object as it moves through air or another fluid. It occurs when the surface of the object disrupts the flow of the fluid, causing friction and resistance to motion. The amount of aerodynamic drag depends on factors such as the shape, size, and speed of the object, as well as the density and viscosity of the fluid it is moving through. In general, objects with smoother surfaces and streamlined shapes experience lesser aerodynamic drag compared to those with rough or irregular surfaces.