PMS refers to a group of emotional, behavioral, and physical symptoms that occur in the luteal phase of the menstrual cycle, typically one to two weeks before menstruation. Common symptoms include mood swings, bloating, breast tenderness, irritability, and fatigue. While the exact cause is unclear, hormonal fluctuations are believed to play a central role. Treatment may include dietary changes, exercise, stress reduction, and medications like birth control pills or antidepressants.