Sometime during puberty girls start their mensturation. After the first menstruation a girl can get pregnant. The menstruation approximatly happens every four (4) weeks.
Words with same meanings
time of the month
When a girl becomes older, a egg developes every month in her ovaries.
If that egg is fertilized by sperm than a baby is created.
For that a thick mucous is formed as a precaution. The egg nests in this mucous.
If the egg is not fertilized this mucous is not needed. Then it disolves. This makes the uterus sore and bleed.
The body uses the blood to flood the mucous pieces out of the body. The vagina is used as an exit.
That is the reason woman normally bleed once a month. The body gets rid of precautions that are not needed in that month.
When woman get older (around 50 years old) the bleeding stops. This means they cannot have children anymore. This process is called the menopause.