The hymen is a very thin and elastic film located at the vaginal opening. Many people think it closes everything off like a seal, but in fact, it usually has an opening (or several) for menstruation to come out. It can stretch or tear for various reasons, such as physical activities, sports, or using tampons. The most important thing to know is that the presence or absence of the hymen does not define who you are or your value as a person.