MedlinePlus, the National Library of Medicine's online Medical Encyclopedia (accessed June 26, 2006), wrote:

“A Migraine is a type of primary headache that some people get repeatedly over time. Migraines are different from other headaches because they occur with symptoms such as nausea, vomiting, or sensitivity to light. In most people, a throbbing pain is felt only on one side of the head.”

June 26, 2006