What do the red lights at the end of a runway signify?

The correct understanding of red lights at the end of a runway is that they signify the end of the runway that the aircraft is facing. These red lights are a critical part of the visual aids provided for pilots during takeoff and landing. When approaching the end of the runway, the red lights provide a clear indication to the pilot that they are nearing the termination of the operational surface. This information is essential for ensuring safe landings and takeoffs, especially in low visibility conditions.

While options that suggest other meanings, such as the beginning of the runway or the center, do not accurately represent the function of the red lights, it is important to note that glide slope indications pertain to vertical guidance during approach and are independent of the horizontal boundaries marked by runway lights.