Guro can be any sort of blood/guts theme, I think extreme forms of vore can cross over and be considered guro (seems more like a rating of extreme violence to me).
Vore is traditionally the swallowing of an intact person or creature. It doesn't have to be oral, either. Um, put it this way, if there is a hole on your body, there is a vore for it. One body goes into another, in some way.