In the context of (GTA V) modding, x64v.rpf is a massive archive file containing thousands of game assets, specifically focused on world geometry, textures, and player-related models. Review of x64v.rpf: The Modder's Treasure Trove
I notice you're asking about a file named — this is a file associated with Grand Theft Auto V (GTA V) on PC. It's part of Rockstar's RPF archive format used to store game assets. x64v.rpf