Menstruation is the process of discharging blood from your uterus, though you may know it by other names like period, menses, monthlies, etc.
If your menstruation has started, congratulations! Menarche, in addition to being a sign of the completion of your puberty, shows promises that there is a healthy functioning relationship between your brain, the ovaries and the uterus. Menstruation shows that you have the potential of becoming a mother in the future, which is a great value.
As you know, all body functions are controlled by the brain. Generally, a natural menstrual cycle begins with the release of follicle-stimulating hormone from the pituitary gland, which reaches the ovaries through the blood. The ovaries, in turn, secrete female sex hormones, which in addition stimulate ovum development growth in the ovaries, and cause the lining of the uterus to thicken affecting the uterine cells to prepare it for pregnancy. If you do not get pregnant, these hormones will drop and the thick lining of cells in your uterus will break down and leave your body. This is the menstrual blood and tissue.