What lights indicate the landing threshold at an airport?

The lights that specifically indicate the landing threshold at an airport are threshold lights. These are located at the beginning of the runway and are typically a set of lights that indicate to pilots the point where the runway begins for landing. They play a critical role in ensuring safe landing procedures, especially in low visibility conditions. Threshold lights are usually white, providing clear guidance to pilots when they are approaching for landing.

Other choices serve different purposes: runway edge lights outline the perimeter of the runway, approach lights assist pilots in the final approach by providing guidance and visual cues as they near the runway, and taxiway lights guide aircraft along taxiways but do not indicate the landing threshold. Therefore, threshold lights are specifically designed for that indication function, making them the correct answer.