Endometriosis is a medical condition in which tissue similar to the lining of the uterus grows outside the uterus, often causing pain and other symptoms. This misplaced tissue can lead to inflammation, scar tissue, and adhesions, potentially affecting fertility. Common symptoms include pelvic pain, heavy menstrual bleeding, and pain during intercourse. The exact cause of endometriosis is still not fully understood, and treatment options may include medication, hormone therapy, or surgery.