There are two control surfaces that can be on the wing. (Actually more, but leave that for now.) Most R/C planes that you see just have ailerons on them. As was said before, they can either be at the ends of the wing or run the full length.

Ailerons are used to "bank" the plane. The proper term is "roll." The ailerons move in opposite directions. When the left one moves down, the right moves up and vise versa. To roll the plane to the right, the left aileron moves down and the right aileron moves up. Air hitting the lowered left aileron pushed the left wing up. Air hitting the raised right aileron pushes the right wing down.

Flaps are another control surface that can be on wings but you don't see them as often. The are more common on war birds. The right and left flaps move in the same direction. In normal flight, flaps are said to be "up" but that means that they are in line with the normal contour of the wing. They have no effect in this postion. When the flaps are lowered, they change the geometry of the wing. More drag is created but also more lift. This allows the plane to stay in the air but fly slower. Flaps are usually used to allow the plane to land at slower speeds.

"Flaperons" are ailerons that also provide the function of flaps. This is done through settings in the transmitter. When the "flaps" are lowered, both ailerons lower. When aileron signals are sent, the ailerons move up or down from the flap postion instead of the neutral.

Hope that helps.