Being a virgin technically means that you have never had sexual intercourse - so both boys and girls can be virgins. However when a girl has sexual intercourse for the first time she loses her virginity and normally her hymen gets torn at the same time. A woman's hymen is a very thin layer of skin at the opening of her vagina which is there when girls are born. Your hymen has a small hole in it which allows for blood to come out when girls start menstruating. If you are a 'virgin' the hymen is still there, but when you have sex for the first time then your hymen gets torn and is no longer there. The first time people have sex when the hymen gets completely torn it can cause some bleeding and there may be a bit of soreness. This varies greatly from person to person and depends, to a certain extent, on how thick your hymen is. However, having sex is not the only way that your hymen can get torn. It may very occasionally happen when riding bicycles, riding horses. It gets torn a bit if you use tampons, but even if this happens you are still technically a 'virgin' until you have had actual sexual intercourse with a man.