Biogeographical studies use information for various fields, such as evolutionary biology, geography, geology, and climate science to determine how organisms evolved through time and how the moving of tectonic plates resulting in forming continents, mountain ranges and islands has affected their distribution.
Studies in this field explain how organisms that now live on different continents are very closely related and how the flora and fauna of islands are connected to one of the closest continents etc.
Lunar maria (plural form of the Latin word mare, which means sea) are dark surfaces that can be found all over the moon (17% of the Moon is covered in them) that have been created as a result of volcanic eruptions. These areas are made up of basalt, and given that they seemed almost waterlike, the astronomers in the distant past mistook them for seas, whence their name comes.
When it comes to craters, their origin is quite similar - volcanic eruptions created them. When lava starts erupting from a volcano, it has to get out from somewhere - and thus craters are created. If you are referring to lunar craters, however, there are many speculations as to how they were created: due to volcanic eruptions, meteoric impact, or glacier activity.
