Which part of the wing is referred to as the back edge?

The trailing edge is indeed the correct answer to identify the back edge of the wing. In the context of an aircraft wing, the leading edge refers to the front part that first encounters the airflow, while the trailing edge is the opposite side, where the air exits after passing over the wing. This area is crucial for the aerodynamic performance of the aircraft, as it plays a significant role in controlling airflow and minimizing drag.

The aileron and flap are both movable parts typically located on or near the trailing edge, but they serve specific functions rather than defining the entire back edge of the wing. Ailerons are primarily used to control roll and assist in maneuvering the aircraft, while flaps are deployed to increase lift at lower speeds during takeoff and landing. Understanding the distinction between these components helps clarify the purpose and function of each part of the wing structure.