Ellison is a lunar impact crater that lies on the far side from the Earth. It is located just beyond the northwest limb , to the southwest of the large walled plain Poczobutt. Due west is the crater Coulomb. The outer rim is roughly circular, with an inward protrusion along the southern rim and a slight outward bulge to the wet-northwest. (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.