Poincaré is a large lunar impact basin that lies in the southern hemisphere on the far side. Most of the formation has been heavily eroded by subsequent impacts, leaving a battered formation with only rugged remnants of the original outer rim to the west. The eastern half has been completely worn away, and much of the interior has been resurfaced by lava flows. This surface has a lower albedo than the surrounding terrain, giving it a dark appearance. (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.