Hansen is a lunar impact crater that is located near the eastern limb. At this location the crater appears oval due to foreshortening, but the crater is actually nearly circular. It lies to the northeast of the larger crater Condorcet, and to the south of the smaller Alhazen. The outer wall is sharp-edged, with a slight outward bulge to the southwest. (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.