EXTRA Virgin?

So, I buy olive oil. All of us, health conscious or not, have heard the benefits of olive oil touted by enough sources that we all have a bottle at home - whether we use it or not.

AND -- (or so I've read) if you want to have the best olive oil experience possible, you want to get the EXTRA virgin kind.

What I want to know is, what makes the olives 'extra' virgin? I mean, if a virgin olive is one that's never 'been with' another olive; what's an extra virgin, one that's never kissed another olive? Or maybe one that's never even crossed vines?

Maybe there's an entirely separate vineyard for the 'extra' virgins. You know, like an olive monastery. Maybe the little olive nuns have to swear a vow of chastity to the mother branch?

If so, then how do we keep getting new olives? I ask only because at the store the only choice for olive oil seems to be either the virgin or 'extra' virgin variety. MAYBE the little hussy olives that procreate are the ones we eat on salads?

(...this train of thought is just a glimpse of what's going on inside my brain when I'm not talking.)