The difference is the mood
One is subjunctive (were) and the other is indicative (are)
While both sentences are indeed grammatically correct, the mood is completely different. A subjunctive mood suggests that there is doubt.
If you were a virgin | subjunctive
If you are a virgin | indicative
The first sentence expresses the uncertainty of Jane's virginity. The same concept goes for these sentences
- If I had one million dollars ...
- If I were rich ...
- If cats were people ...
Using the million dollar sentence as an example, it's very clear that the subject does not have a million dollars, and there is usually a conditional phrase that follows, but that's another beast on it's own. You have to use the conditional because the first statement is in fact subjunctive.
If I had one million dollars, how would I spend it?
If fish could walk, fishing would be quite easy.
If a tree fell in the woods, would it make a sound?
If the student had read the book, he would have passed.
The root word here is indicate, which means to point something out, to demonstrate an actual, factual action... or being.
I have one million dollars
By using the indicative mood, there is no uncertainty, and there would be no need to use conditional phrases afterwards.. you cannot say
If I have one million dollars, how would I spend it? INCORRECT
The sentence would be the epitome of a grammatically incorrect sentence. It is very clear from the sentence that I do have one million dollars, no doubt whatsoever, no hopes, nothing..
If I have one million dollars, I will spend it. CORRECT
If a tree falls in the woods, does it make a sound?
Any doubt would be expressed in subsequent sentences.
John : Jim, I just heard that you won $1 Million!
Jim : John, if I have a million dollars, then where is it?
Can you spot the subjunctive sentence?
If cats are people, then why can they not talk?
If cats were people, then they could talk.