@Killer979 In fact to use any mod you'll need the related game, whatever it's a virtual version or the disc version as said @Jitnaught
(note that mod not often work on pirated game, and that modder mostly don't support the pirated game)
A mod, is a modification bring to an existing game in order to add/adjust/remplace thing in it.
So mod for gtaV will only work if you've the GtaV game,
mod for Skyrim will only work if you got Skyrim game
mod for fallout will only work if you got fallout Game
(note that this website only concern mod about gtaV )