Langley is a lunar crater that is located close to the northwestern limb , and from the Earth is viewed edge-on. It is located in the gap. Just to the northwest is Stokes. The rim has been heavily damaged by nearby impacts, and the result is an irregular perimeter that has been reshaped and heavily eroded. (wikipedia entry)
A crater is a circular depression likely created by an impact event. On the Moon they are named after deceased scientists, polar explorers, astronauts or cosmonauts.