VR Porn can be both. The idea behind VR porn is to make you a part of an experience as though you are an active participant. So just like in real life, that could mean being a fly on the wall at a sex party, or it could mean you yourself being the center the attention.
I've never tried it, but I'd like to give it a go. I think it could be a great way for people to experience fantasies that they might not want to do in real life. It doesn't have to be just for solo play either, its could work for couples to experience the VR environment together.