A p3p file extension is related to the W3C Platform for Privacy Preferences files.
P3P file extension - W3C Platform for Privacy Preferences data
What is p3p file? How to open p3p files?
File type specification:
The p3p file extension is associated with the W3C Platform for Privacy Preferences that enables Websites to express their privacy practices in a standard format that can be retrieved automatically and interpreted easily by user agents.
This p3p file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.