An airfoil is a specially shaped structure designed to generate lift when air flows over it. Commonly found in aircraft wings, propellers, and turbines, an airfoil typically has a curved upper surface and a flatter lower surface. This shape allows air to move faster over the top, creating lower pressure above the airfoil and higher pressure below, resulting in lift. The effectiveness of an airfoil depends on its design, including factors like its angle of attack and aspect ratio. Engineers use principles of aerodynamics to optimize airfoils for various applications, ensuring that they perform efficiently in different flight conditions and speeds.