Evolution of a Wing.
Peter Hanely, cal at splitreflection dot com (take that, spambots)

Lets start with a really sinple wing section.
(image, flat plate)
Yes, a simple flat plate at an incline to the airflow.  Aerodynamically it works very well.  Structurally it needs help.
(image,  thick wing)
Here we have something closer to a wing as used by real aircraft.  The smooth rounded nose and sharp trailing edge make it about as good aerodynamically as the flat plate.  The thickness allows it to hold its shape sticking out.
(image, stall)
The more you tilt the wing, the more lift you get, to a point.  Too far and airflow seperates from the upper surface.  The wing stalls.
(image, cambered flat)
Curve (or camber) the wing and you can get a lower angle at the leading edge, avoiding stall, with a higher angle at the trailing edge, producing more lift.
(image, flat plate flap&slat)
While the simple curve produces lots of lift for slow speeds, it doesn't do so well at high speeds where a flatter wing can produce the needed lift.  As a compromise, a lesser curved wing may have leading or trailing edge slats and flaps, aproximating a high camber  wing for low speeds, and a flatter wing for high speeds.
(image, flex flat)
Desirable, but not easily built, a wing with variable smooth curve would provide good performance and high and low speeds.
(image, complete wing section)