Role of Camber in an Aerofoil

Camber is defined as the convexity of the curvature of an Aerofoil from leading edge to the trailing edge. It is the fundamental component of Aerofoil design which varies with the volitional speed, strength and purpose of the Aerofoil. The Greater the camber of the center line (line equidistant from leading and trailing edge) the more convex will be the upper surface. When upper and lower surfaces are mirror images, that leads to the mean camber line to be coincident with chord line then, airfoil is called as uncambered airfoil or airfoil of zero camber. 

Uncambered Airfoils are also known as Symmetric Airfoils as mean camber line coincides with the chord line.

Camber creates a pressure difference between the upper and lower surfaces of the airfoil even at zero angle of attack, as air flows at a higher velocity on the upper surface compared to lower surface which creates a low pressure at upper surface and high pressure at lower surface, due to which there is a generation of lift in cambered airfoils at zero angle of attack.

Since, in Symmetrical or uncambered airfoils there is no such camber so the pressure difference is zero at zero angle of attack which results in no lift at zero angle of attack in symmetric airfoils.