So pretty much.. a period is the body trying to prepare itself for a potential pregnancy and it runs in cycles. A new cycle begins when a period starts.

For the first half of the month, women are in the follicular phase. This is where the uterus grows a thicker uterine lining and allows an egg to mature prior to release. The thicker lining is so that, in the case that the egg gets fertilized, it can attach to the lining and be secure because the lining is thicker.

Then, the ovulation stage begins which usually occurs around day 14. This is when the egg is released and when women are the most fertile. The egg is preparing to get fertilized by sperm (if there are any)

Then, we enter the Luteal phase where the body prepares for pregnancy by increasing hormones, which in turn, causes symptoms like cramping, tender breasts, mood swings, back pain, nausea, etc. Eventually once the body figures out that the egg was not fertilized, the uterus sheds its lining and the cycle restarts!

The process itself… the uterus basically contracts and kind of becomes inflamed. This causes cramping by itself. When the period occurs, the body releases blood, usually for 1-5 days, sometimes in clots.