Buch is an old, worn crater that is located in the rugged southern highlands. It lies to the northeast of the large crater Maurolycus, and the comparably sized crater Büsching is attached to the northeast rim. The crater rim is slightly elongated in the northeastern direction, and forms an egg-shaped depression in the surface. The rim has been eroded by many lesser impacts so that the edge is rounded and worn down, and the crater forms only a low depression in the ground. (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.