I am currently re-reading the Lord of the Rings. While reading the chapter "In the House of Tom Bombadil", where the four hobbits meet Tom and Goldberry, I thought a lot about the speculations and questions about who Tom Bombadil actually is. Then the question "Who exactly is Goldberry?" struck me. From the description in the book I am not able to deduce if she is an elf or maybe a Maia, or - like Tom - probably something different entirely.

So who exactly is she? And what else is known about her, apart from the (little) information given in FotR?