Ovarian cysts are sacs filled with fluid that develop on or inside an ovary. Most women will develop at least one at some point, often without ever knowing it, since many cysts cause no symptoms and disappear on their own within a few months.
Most cysts are related to the normal menstrual cycle and are harmless. Less commonly, cysts can grow large, twist, rupture, or be linked to an underlying condition, which is why persistent or unusual symptoms are worth getting checked.