In earlier posts I've likened the courses on FutureLearn (don't call them MOOCs) to a good hardback book. This misses a crucial element: the connectivity with other students (I prefer to call then participants). I would therefore say, looking for a few lines to explain the appeal to the ignorant, that it is like joining a book club: everyone has the same thing to talk about.
The current course that I love is "Exploring Filmmaking' - storytelling is universal, and that's what this is about. 'Boyhood' winning the BAFTA last night also reasserted the joy, pleasure and value of stories about our lives as they are without special effects, superheros, drugs or murder: Growing up is drama enough.