Headache is a common symptom that can have various underlying causes like tension, migraines, or clusters. Tension headaches involve muscle tension and are typically mild and bilateral. Migraines are more severe and often unilateral, involving nausea, sensitivity to light/sound, and possible aura. Clusters occur in repeated daily episodes over weeks to months. Diagnosis is based on symptoms and history. Treatment focuses on prevention through medications that reduce vascular changes, muscle tension, or other triggers, as well as acute relief of pain.