A de Laval nozzle is a specially designed tube used to accelerate gases to supersonic speeds. It has a converging section that narrows down, followed by a diverging section that expands. As gas flows through the nozzle, it speeds up as it passes through the narrowest point, known as the throat, and then continues to accelerate in the diverging section. These nozzles are commonly used in rocket engines and jet engines to improve thrust and efficiency. By converting thermal energy from combustion into kinetic energy, the de Laval nozzle plays a crucial role in propulsion systems for various aerospace applications.