Zeno is a lunar impact crater located near the northwestern limb. It lies to the east-southeast of the crater Mercurius. Farther to the east , along the limb, is the well-formed crater Boss. The rim is slightly distorted and has received some erosion due to subsequent impacts. (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.