I try to leave software to the software geeks, but now and then I just have to sit down and figure it out. As I recall, these terms not only mean something different in software, but they are either reversed, or the one means the other, and the other means something which has no equivalent in hardware. Or something equally confusing. (I was originally exposed to all four at the same time, with no tech background at all, and it left a scar..)
Back to hardware, I tend to think V&V are related, in that you shouldn't validate until all your verification is done and looking good. I also tend to think of validation as the cherry that sits prettily atop the verification cupcake. As for a gap, my only knowledge of this is as an indicator that something has not gone well in verification, so it's usually a gap filled with design engineers whispering among themselves, hoping they can get it sorted out before the next status report is due, along with silence from me and the product manager, as we hope for the same thing and are restraining ourselves from asking. Otherwise, not a gap so much as a another step, which is (hopefully) a design review.