What does the camber line in an airfoil represent?

The camber line in an airfoil represents the shape of the airfoil and specifically defines the mean line that runs from the leading edge to the trailing edge. It is an important factor in aerodynamics as it indicates the distribution of airflow over the upper and lower surfaces of the airfoil. The camber line can be used to determine the lift characteristics of the airfoil; a greater curvature can lead to increased lift at a particular angle of attack.

The other options do not accurately describe the camber line. The angle of attack refers to the angle between the oncoming air and the chord line of the airfoil, which is distinct from the shape of the airfoil itself. The span of the wing refers to the distance from one wingtip to the other, an entirely different measurement. Thickness refers to the dimension of the airfoil from its top surface to its bottom at any given point, which is also separate from the concept of the camber line.