What does the mark of the moon mean?

It is an APP that records the menstrual cycle of girls.

Nowadays, many people don't like to talk about menstruation directly. After all, girls are generally a little shy. If you call yourself menstruating in public in the hall, you will be laughed at. Therefore, modern women will give menstruation a lot of nicknames, making it sound less direct, making people feel embarrassed that girls have their period, and always say that their period is coming. Menstruation, also known as menstrual cycle, is a physiological cycle, which occurs between some fertile female humans and other animals, while other mammals experience estrus cycle. In women of childbearing age and primate females, the endometrium undergoes periodic changes such as autonomous thickening, vascular proliferation, gland growth and secretion, endometrial collapse and bleeding and shedding every other month. This periodic vaginal bleeding or uterine bleeding is called menstruation.