i guess i probably downloaded a VOB mod and now that i know it's against the rules, so can some give me the default version of the fz50?

I've seen some threads saying that VOB mods are bad and illegal and so. I don't get it when ppl try to explain to me wut they are. I've downloaded some mods for an r8 and a challenger and so. Is that considered a VOB mod? If so, wht are the legal mods there are?

whats a VOB mod?