An original research article is a detailed study reporting original research conducted by the author. It includes hypothesis, background study, methods, results, interpretation of findings, and a discussion of possible implications. Original research articles are usually long articles.
A letter is a short scientific article that only includes a particular aspect of a scientific problem. It is, in effect, a shorter version of an original research article.
A perspective piece is a scholarly review of fundamental concepts or prevalent ideas in a field. Perspective pieces usually present a personal point of view critiquing widespread notions pertaining to a field. These are usually short articles. A perspective piece is very similar to an opinion piece or a commentary, and these terms are often used synonymously.
Nature Geoscience does not mention perspective as an article type, but it does mention commentary. It also mentions that the commentary section is the opinion section of the journal. Therefore, if you plan to write a perspective piece, you should be able to submit it under the article type “commentary.”