There are lots of ways to describe the differences between xMOOCs--the courses produced by edX,Coursera, and Udacity starting around 2011--versus the cMOOCs--the original courses dubbed MOOCs in 2008 and 2009 by a number of university professors, mostly in Canada.
One of the best ways to distinguish between them is by thinking about their "killer app," the special tool that distinguishes them from previous generations of technologies.
