What is a berm and what does it represent?
A man-made Earth dam.
A berm is a built up strip of earth that works as a dam. There used to be other uses for a berm, like in battlements, but nowadays it is used as a dam. The reason it is used verses a stone or concrete dam is you can plant on a berm, so essentially it can be a nice part of a garden or yard and still serve the purpose of a dam.
This is sort of an extreme example of a berm that does not have any vegetation planted on it (yet).