What's the difference between...?

a terrorist and a revolutionist? I know the literal definition between the two, but there seems to be a gray area. I often hear Che Guevara was a revolutionist, but it is known that he killed many people so wouldn't that make him a terrorist and not a revolutionary? Or the Hmong that fought against their own country to help the US and are considered terrorist as defined by the Patriot Act. Anyone have any insight? Thank you.