Daniell is a lunar impact crater located in the southern half of the Lacus Somniorum. To the south-southeast is the much larger crater Posidonius. The Rimae Daniell rille system are to the west crater. The rim is oval in form, with the long axis oriented north-northwest to south-southeast. (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.