Lateral motion of an aircraft is the rolling motion that an aircraft makes around a centerline running from the front to back of the aircraft (the longitudinal axis) that raises one side of the aircraft as it lowers the other. When the Wright brothers first started flying gliders, they had not yet seen the need for lateral control (roll) although they already understood that a mechanism for controlling the upward and downward motion of the craft was important (pitch) and a way to control the side-to-side motion was necessary (yaw). An elevator would control the pitch and a rudder would control the yaw.
The need for lateral control became obvious only after they took to the air and had achieved sufficient lift to fly for more than a few seconds. Then they realized that there had to be a way to compensate for winds coming at the aircraft from the side that could cause an aircraft to lose control. Lateral control was also needed so that the pilot could bank—lift one wing or the other to make the craft turn so that it would be headed in a different direction. Lifting the right wing would tilt the aircraft downward on the left and turn it left. Lifting the left wing would tilt the aircraft downward on the right and turn it right.
Credits - Civil Air Patrol
The Wrights solved the problem of lateral control through "wing-warping." Wing warping twisted the wing slightly, resulting in a banking motion of the aircraft. This both allowed the aircraft to turn and allowed the pilot to compensate for gusts of wind that came from the side. Wing-warping and the entire concept of lateral control was spelled out in their 1906 patent.