A screw propeller, commonly known as a propeller, is a device with blades that rotates to create thrust, propelling a vessel through water or an aircraft through air. It operates on the principle of converting rotational energy into linear motion, allowing boats and planes to move efficiently. Typically made from materials like metal or composite, screw propellers come in various sizes and designs, depending on their application. They are often used in conjunction with engines, such as those found in ships or aircraft, to enhance performance and maneuverability.