A period is the bleeding that happens from a woman's vagina which occurs when the lining of a woman's womb (uterus), made up of blood and some cells, comes away naturally. When women start having periods this is called menarche and a period is called menstruation. Menopause is when women stop having periods. There are lots of other different names given to periods like - the curse, the monthly, time of the month, the rag, and many more. Periods in a woman are controlled by the release of her hormones in her blood stream.