Named after Johann Bayer - German astronomer (1572-1625).
Bayer is a lunar impact crater located in the southwest section of the moon, to the east of the crater Schiller. The rim is slightly worn by erosion, but remains well-defined. There is an inner terrace, but the outer wall is intruded upon by nearby impacts. The most significant of these is Schiller H, which forms a ridge attached to the northwest rim. (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.