Most of a woman's genitals are tucked inside her body. Behind the labia is a tube called the vagina, which cannot be seen on the outside of the body. (People often incorrectly use the word "vagina" to refer to the vulva.) When a man and a woman have sexual intercourse, the man's penis is placed into the woman's vagina. When a woman menstruates (has her menstrual period), blood and other fluid from the uterus pass out from her body through the vagina. If a woman uses a tampon (a specially-made wad of material) to absorb this fluid, she puts it into her vagina. The vagina is also called the birth canal, because when a pregnant woman has a baby, it passes through the vagina.