A MOOC – a «massive open online course» is an online course aimed at unlimited participation and open access via the web. In addition to traditional course materials such as filmed lectures, readings, and problem sets, many MOOCs provide interactive user forums to support community interactions. Some later MOOCs use closed licenses for their course materials while maintaining free access for students.
Many MOOCs use video lectures, employing the old form of teaching using a new technology. Because of massive enrollments, MOOCs require instructional design that facilitates large-scale feedback and interaction. The two basic approaches are (1) Peer-review and group collaboration, and (2) Automated feedback through objective, online assessments, e.g. quizzes and exams.
So-called connectivist MOOCs rely on the former approach; broadcast MOOCs rely more on the latter. This marks a key distinction between cMOOCs where the 'C' stands for 'connectivist', and xMOOCs where the x stands for extended (as in TEDx, EdX) and represents that the MOOC is designed to be in addition to something else (university courses for example).
Assessment can be the most difficult activity to conduct online, that's why MOOCs often use the approach of a final examination as presence (face-to-face) event and the need to finalize the course with a personal written exam.
As MOOCs are more appropriate in the academic environment, GIZ uses for it's ACWUA-WANT program rather the format of tutor-acompagnied courses – they are more suitable to the context in developing or newly industrialized countries.
[Source: en.wikipedia.org (partly)]
[watch this 2013 video by the The New York Times explaining the term MOOC]