What's the difference between migraine and headache?

The article "Making Headway on Migraines" on page40, January 28-29, is talking about symptom, misunderstanding, treatment of migraines, and after reading this article, I'm curious about one question: are migraine and headache the same or different? It seems that migraine could make someone more suffering than headache. So, does anyone know what's the difference between migraine and headache?