Well, I'm not "on staff" but I think I can help you out here.
Casual sex usually means sex between two people who aren't really in a committed relationship, even to the point of one night stands (just being with someone for a night) and such.
Born again virgins are, as I understand it, people who have had intercourse or sexual experienece but have decided not to have intercourse again (usually until marriage), often through counseling with their religious organization. I tend to associate the idea of born again virginity with religion.
If a person "is saving themselves for marriage" they probably mean they aren't going to have intercourse until they are married. It's a personal choice, and based on the idea (in my estimation) that virginity is a gift to give their future spouse and only their future spouse.
I hope that answered your questions.
I see you shiver with antici......pation