What does it mean to pop your cherry?
Popping a woman's cherry refers to losing her virginity. There is a fine membrane in the vagina of girls called a hymen. The first time she has sex, the man's penis will likely tear the hymen, and she may bleed when this happens. So the term comes from the color of the blood and how easy this membrane can be ruptured.
However, not all women have a thick hymen nor bleed the first time they have sex. It is also possible that something besides sex can tear the hymen such as riding a bicycle or wearing a tampon. This is something important to note since if a woman doesn't bleed the first time she has sex, it does not always mean she has had sex before. In some places in the world, there may be serious consequences if a woman is accused of not being a virgin before marriage, and it is not fair if the woman wasn't born with much of a hymen or somehow injured herself and caused it to tear prematurely. That can create scandals, so there are even ways to surgically replace the hymen or fake the bleeding in such parts of the world.