: This is a popular "feature" or tool that acts as a container for your mods. It allows you to add new clothing and player slots without having to constantly modify the massive x64v.rpf file directly, bypassing the 4GB limit and providing extra slots for the main protagonists.
For developers and power users, here are the technical details of x64v.rpf as seen in the latest version of GTA V (as of the 1.0.335.2 patch): x64v.rpf