The shape of the wing directly affects every aspect of how the plane flies from the speed of the plane to the rate of acending and descending altitutdes. When a plane is being prepared for landing the shape of the wing helps the plane slow down and reduce the amount of lift force that is being appled under the wing to keep it in the air.

The shape of the wing changes because as the jet slows, it needs to produce more lift at approach and landing airspeeds. When an airplane lands it is desirable to fly as slowly as possible. Ideally for landing, an airplane would have a large wing with a very cambered airfoil. However, airfoils designed to perform well at slow speeds are not good for flying at faster speeds, and vice versa. Airplane designers have developed a set of features that allow the pilot to increase the wing area and change the airfoil shape to compensate for this. Lift = pressure x area The way to increase the amount of lift a wing can produce is to increase it's surface area. Leading edge slats & trailing edge flaps do this. Flaps allow an increase in approach angle on landing, without increasing airspeed as the nose is lowered on the approach. When flaps are extended, they increase the camber or curve of the wing. The top surface the wing has more curve than the bottom surface, so air molecules that travel over the top of the wing are sped up due to the 'venturi' effect of the camber. This acceleration causes a drop in pressure in the air mass on top of the wing causing 'lift'. Read more on the subject at these selected links- Wing Design- http://virtualskies.arc.nasa.gov/aeronautics/tutorial/wings2.html About High Lift devices- http://sandboxv3.erau.edu/er/newsmedia/articles/wp1.html Kinds of flaps- http://en.wikipedia.org/wiki/Flap_%28aircraft%29 About Slats- http://en.wikipedia.org/wiki/Slats

There are a few principles about wings and aerodynamics that you need to understand for this question. The way a wing behaves in flight is dependent upon the wing design and what the plane is doing. * * * First of all: a quick definition of lift: Lift is not a push. It is a 'suck'. As air passes an aerofoil, it splits into two halves. One half flows over the top of the wing, the other half flows over the bottom. Now, if the air on one side has to go further than the other side, it has to flow faster. This is why the wings are curved. The curve on top creates a longer distance to the rear than the flat bottom. The air on top has to travel farther, hence faster. As air speeds up, its pressure decreases. So, what you have is an area of low pressure above the wing that 'sucks' the wing up. This is lift. * * * Draw an aerofoil shape (like a side view of a wing). Now, draw a line from the front tip to the rear tip. This is called the 'chord' line. There are several principles that flaps and slats control on a wing: thickness ratio, camber and angle of attack. Thickness Ratio: compare the thickness of your aerofoil above the chord line compared to the thickness beneath. This is your thickness ratio. A thicker top half means more of a curve and a longer surface. The greater the curve, the faster the air has to travel, and the greater the lift. Camber: is a function of the shape of the wing. Remember the 'chord' line? Good. Now, if you were to draw a curved line from front to back, keeping it at the exact mid-point between top and bottom, you have your camber. (i.e. a curved line that exactly cuts the wing in half top to bottom). The sharper the curve of this line, the greater the camber. Greater camber means greater lift, and greater drag. Angle of attack: is the angle of the wing leading edge compared to the airflow. If the air is meeting the leading edge dead on, then the AoA is zero. Most aircraft are designed with a natural straight and level AoA of between 4 to 6 degrees (the air hits the leading edge at 4 - 6 degrees below level). This small angle helps with airflow over the wing. Increasing this angle - to a certain degree - increases lift and drag. When the aircraft maneuvres, the AoA increases, because the air is coming in from above or below the wing. At a certain point, though, the angle becomes so sharp that the air cannot follow the path over the top of the wing, and just swirls around in what's called turbulence. The wing loses lift because there's no air to cause the low pressure on top. This is called a stall. Now, how does this relate to flaps and slats? Flaps and slats alter all three of these properties. On your original aerofoil picture, draw in a flap coming down at 45 degrees from the rear of the wing. Now draw a much smaller flap coming down at, say, 30 degrees from the front of the wing (This is the slat). Now, draw another straight line between the tip of the slat and the tip of the flap. This is your new chord line. Compare the "thickness ratio". With flaps down, this creates a much greater area on top of the wing. The air has much further to travel, which speeds it up even more than before. This produces more lift. It also produces much more drag. You'll hear pilots actually power up their engines to keep their airspeed when they drop flaps. So yes, within reason, flaps can be used to slow and aircraft - but there are limitations to that. Compare the Camber. If you were to draw a line keeping halfway between the top of the wing and the chord line, you'll see a much sharper, much longer curve. Again, greater lift. Now, for Angle of Attack. Since an aircraft will actually start to slowly 'sink' through the air as it comes in to land, the angle of attack increases. (If you can't imagine this, hold out your hand as if it's a plane. Push it straight forward through the air. This is straight and level flight. Now, keeping it level as before, push it forward but slowly downwards as well. Notice how it 'sinks' as it moves forward? This is how a plane comes in to land). The air approaching the wing is not coming from straight on anymore, but rather from below. Depending on how great the 'sink rate', the Angle of Attack could get up to 20 degrees or more below level. This is the region where the wing might stall. Solution? Droop the wing leading edge so that it points down into the wind flow. This is what slats do (as well as increasing camber and chord). Example: if you had 20 degrees Aoa and drooped the slats down 15 degrees, then you now only have an effective AoA of 5 degrees - right back in optimum range. So put simply, flaps and slats increase lift at low speed, increase maneuvrability at low speed, lower the speed at which the aircraft will stall, and allow it to maintain greater angles of attack for landing. The only other extra flight control (apart from ailerons) you might see on a passenger plane are spoilers. They are the flat flaps that pivot up from the top surface of the wing. These ARE for reducing lift and speed. Basically they can be used on either side to cause that wing to lose lift and drop, which rolls the plane, or both sides together, which acts more like an airbrake. You'll notice them pop up just a little bit when they are used for maneuvring, but when you hit the runway you'll see them pop up almost vertical. Once on the runway, the pilot will reverse thrust - so you'll hear the engines wind up to full power again, and the wheel brakes will come on, as well as the wing-spoilers. The result: most passenger aircraft can stop in a shorter distance than it takes them to take off. I hope all of this isn't too complicated, but it's about the simplest way I could break it down.