Cajal is a tiny lunar impact crater on the northern part of the Mare Tranquilitatis, in memory of the Spanish doctor and Nobel laureate Santiago Ramón y Cajal. Cajal was formerly designated Jansen F, prior to renaming by the IAU. Also to the northwest is a system of wrinkle ridges designated the Dorsa Barlow. (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.