Machinima?

I have become very confused by the term machinima. I think this article should have defined the term, because I used to think that it only applied to videos created from videogames with a story, like a movie, but Lowood talks about a bunch of other types of videos and fails to really classify them as separate or part of machinima. The internet didn't really give me a straight definition, either...

Anyway, I still found the article interesting. The topic of JuniorX struck a bit of a familiar chord with me. I recently watched a whole lot of Starcraft II beta footage before I got a beta key, much like those interested in WoW watched JuniorX's videos. While I'm not sure if this would be classified as machinima, I have been watching many SCII shoutcasts (HDstarcraft's channel, for example). These served to get me up to speed on how the game works and is played before I had a chance to play myself. I also am able to see new strategies that I can employ in-game.

JuniorX's Dancemovie reminded me of dance parties in WoW. I only played it for a little less than a year, but it was a fun game. As Lowood said in the article, a little bit of game knowledge goes a long way in helping to understand videos made about the game. Of course, some videos require no real game knowledge, like Leeroy Jenkin's famous charge.

So, help me out... What exactly is machinima?