Production of lift is dependant primarily on airspeed, angle of attack and aerofoil design. A fundamental component of aerofoil design is the camber which will vary with the intended speed and purpose of the aerofoil. The upper surface of the aerofoil will always have a positive camber while the lower surface may have a positive (convex), zero (flat) or negative (concave) camber as appropriate for the intended use. An aerofoil in which the camber of the upper and lower surfaces are the same is referred to as symmetrical and is most often found in aerobatic aircraft intended for inverted flight. A supercritical aerofoil will usually incorporate a negatively cambered lower surface. Designers may also vary the camber over the span of the wing to improve stall and stall recovery characteristics.
Explanation of the different types of camber. Source: NASA