Gives you a rough magnetic heading so you can line up easier and keep your pattern straight. Also to tell others which way you’re going to keep from crashing head-on (a north/south strip might be 36/18, for example, so ppl know which way you’re going).

A runway with two ends. And you’d probably be surprised how easy it is to choose one end when you mean another.

Also to identify it from the air as a runway. It’s paved and they painted a centerline; I would have also painted numbers and thresholds.