Like leadwolf said, it is technically called fowl pox, but it is basically chicken pox and a lot of people call it that I guess 'cause it's easier for other people to understand. When you tell some people that your flock has "fowl pox" they go "Well, if a chicken is a type of fowl, then it could be called chicken pox, although they are two different things, which makes it kind of confusing if we did it that way... Now I have to ask, why do they call it chicken pox?

There are 2 forms of fowl pox:
Dry pox, with is spots on their combs, wattles, and face area. It is rarely fatal.
and Wet pox, which show not only on their face area, but in their throats, on their tongues, etc. It makes it very difficult for the chickens to breath, eat, drink, etc. It is often fatal.
Mine have dry pox, thankfully. And I haven't lost to it yet. Though I do have some chicks that I'm a little worried about, but they seem to be okay right now.