Summarize this article:

During the monthly cycle, one or both of a woman's ovaries release an egg. Cysts can form in the ovary because of hormonal problems or imbalances, an obstruction to fluid flow, an infection, conditions producing a chronic inflammation such as endometriosis, inherited conditions, pregnancy, age, and a number of other causes.  Ovarian cysts are quite common in women during the reproductive years and most have no symptoms. These are called functional cysts. Most of the time, functional ovarian cysts resolve without treatment. Ovarian cysts are less common after menopause and do put any postmenopausal woman with cysts at a higher risk for ovarian cancer. Functional cysts are either follicle cysts, which occur in the area of the ovary where individual eggs mature, or corpus luteum cysts,  which occur in what is left of an empty follicle after the egg has been released. These are a normal part of the function of the ovaries. Most follicle cysts are painless and disappear in one to three months. Corpus luteum cysts usually disappear in a few weeks, but can get large, get twisted, bleed, and cause pain. Corpus luteum cysts can be caused by drugs (like clomiphene) used in fertility treatments. There are other types of ovarian cysts that nonfunctional. This means that they are not related to normal ovarian function. These cysts may be painless or cause pain. They include:  Endometriomas: These cysts are generally related to a condition called endometriosis where uterine tissue grows outside the uterus. Dermoid cysts: These are formed from embryonic cells from the woman, not from a fetus.  These are usually painless. Cystadenomas: These cysts can be large and filled with a watery fluid. In Polycystic Ovary Syndrome (PCOS), a large number of cysts are formed. This is a condition very different from having a single ovarian cyst.

Summary:
Learn the causes of ovarian cysts. Know that functional cysts are not serious. Identify nonfunctional cysts.