An airplane can change its direction of travel in several ways. First of all there is pitch which is the up and down movement. This is controlled by the elevators located on the horizontal stabilizer. Next there is roll which is the left and right movement. Roll is controlled by the ailerons which can be found on the back edge of each wing (usually towards the end). The ailerons work in opposite directions causing one side of the wing to create more lift and therefore rolling the aircraft in the given direction. And finally there is yaw which is the side to side movement. This is controlled by the rudder located on the vertical stabilizer (or tail) of the aircraft. Of course all of this is much simpler to understand in a diagram which can be found through a quick Internet search for "Yaw, Pitch, and Roll".