What does that mean? Almost nothing in comics. However, in real life clones don't look like the original person more than a close relative, and obviously, they don't share memories. But in real life, a duplicate like what the Carnage creature made, would look exactly like Gwen, would have the same memories as Gwen and for all intents and purposes, would be Gwen. In fact, some theories about how to make a teleporting machine state that it would only be possible by scanning the subject and then sending the information to a far away place to then make a duplicate using local matter. The original subject would get destroyed/killed in the process. So, if you don't think this kind of duplicate is the real you, try to not get teleported in the future .
As for the crossover itself: I think it's lame. I know that Joe Quesada has a right to change his mind about what he said years ago, but why he has to change it with the things I agreed with? Why can't he change his mind with the stuff I dislike (and no, it wasn't One More Day)?
Whatever. I'll probably read it anyway, but only if I can borrow it from someone or buy it if it really gets good reviews from someone I trust. Can't be fairer than that.