Likely refers to "Player vs Player" in gaming, "Private" (as in Private Vendor/Partner), or a specific project code. RE: Often stands for "Report," "Research," or "Revisions." 2021.39287: Likely a tracking number, ID, or date code.
Without specific context or access to the file contents, this is an archival file and not an essay itself. 2021.39287-PVP-RE.rar
If you downloaded this from a specific project management site, university portal, or game forum, check the source link for description details. Likely refers to "Player vs Player" in gaming,
Use file archiver software such as WinRAR or 7-Zip to extract the files within the .rar archive. "Private" (as in Private Vendor/Partner)