This article deals with the types of correspondence and documents used in the sphere of diplomacy, their differences and functions. The article collects the opinions of various scholars and specialists on the classification of different types of correspondence and documents conducted in the field of diplomacy into large and small groups. Depending on the type of document, theoretical views on its functions are presented at the same time. The linguistic features of diplomatic documents may vary depending on their specific functions and purposes, as they are tailored to effectively communicate and convey important information between different countries and governments. This article also pays attention to lexicosemantic, functional and methodological aspects of diplomatic correspondence. Any diplomatic correspondence, along with being the most important information document, has its specific structure. For this reason, we considered it appropriate to study diplomatic documents in groups, and in this article we have reflected our thoughts and views on this issue.