Multiple sclerosis (MS) is an autoimmune disorder where the body's immune system attacks the protective sheath covering nerves, interfering with communication between the brain and body and potentially causing deterioration of the nerves. MS affects over 400,000 people in the US and 2 million worldwide, making it the most common neurological disorder for those under 40. While its triggers are unknown, factors like genetics and sunlight exposure are thought to contribute to MS, which has varying symptoms and an unclear diagnosis process involving MRI and other tests. Current treatments aim to modify the disease course and relieve symptoms, though MS remains incurable.