Female reproductive system consists of two ovaries which produce and store eggs, two tubes called as Fallopian tubes, uterus and vagina .
An ovary produces eggs which when meet with sperm gets fertilized. It also produces female hormones like Estrogen and Progesterone. Ovaries are located in pelvic cavity that is in the lower abdomen. They are situated at both the side of uterus.
During every monthly cycle (menstruation), follicle grows and matures. This follicle ruptures to release egg. If this fails to rupture then follicle Cyst can form. But, even if it ruptures to release egg (ovulation), the remnant may sometime fail to dissolve causing corpus luteum Cyst. These Cysts are called Follicular Cysts and are related to process of ovulation. These Cysts are harmless, mostly asymptomatic and dissolve within next few cycles.
If fertility drugs are used to enhance fertility in women who are trying to conceive, then these drugs can also cause multiple large Cysts. This is called as Ovarian Hyper-stimulation Syndrome . These Cysts go away mostly.
It is important to remember that complex cysts, in women who have crossed their menopause, can be cancerous and must be thoroughly checked.