The term "XXV20" does not refer to one standard text but appears in different contexts, ranging from UN environmental policies, specifically Decision XXV/20 of the Montreal Protocol regarding financial reports and budgets, to legal, psychological, and technical contexts, such as the 1977–1978 Seminars of Jacques Lacan or a file in RAR archive format. If you've found a "XXV20.rar" file, it's a compressed file containing content you'll need to extract with a tool like WinRAR or 7-Zip, and you should take caution if the source is unknown, as such files can sometimes contain malicious indicators.