It's probably sort of like a party focused fashion and art featuring the music of ARTPOP. I mean, I doubt it'll be too much like an actual rave - she probably calls it "artRave" because of the electronic dance theme of the album as a whole.
Guys, calm down. You know how Gaga is with her new work - she wouldn't let anyone get it early no matter what. ARTPOP is safe inside her laptop and probably encrypted to hell and back.
I hope Gaga gets back into her typical hype mode. She should post the single cover a day or two before the premiere plus a little snippet.
If she's performing at the VMAs, they should announce it on the day the single drops. They can be like, "Lady Gaga will be performing her new song *Gypsy* at the VMAs" to give it more promo.