Courtney is a tiny lunar impact crater on the Mare Imbrium, a lunar mare in the northwest quadrant. It lies about two crater diameters to the northwest of Euler, in an otherwise isolated stretch of the mare. The dark surface in this region is marked by Euler's ray material. (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.