Krieger is a lunar crater on the eastern part of the Oceanus Procellarum. It is located to the north-northwest of the flooded crater Prinz, and north-northeast of the prominent ray crater Aristarchus. To the northwest lies the small Wollaston. In the past the floor has been flooded by basaltic lava, leaving only a low, circular, somewhat polygonal ridge formed by the rim. (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.