When a female virgin first has vaginal intercourse, or some object is inserted into the vagina, causing the
hymen to
rupture, resulting in bleeding. The term "cherry" is used to refer to the red of the resulting blood. However, not all women are born with a hymen, and certain hard physical activities may cause the hymen to tear. Though no surgery can restore virginity (i.e. you can't 'un-have' sex) there is
a procedure to restore the hymen to its original state.