Ever since massive open online courses (MOOCs) started in 2008, we have witnessed six exciting years in the world of education. A new education landscape has come into being and the time has come to take a closer look at its defining features. This book presents some straightforward keys to understanding the MOOC movement. We aim at providing readers with a clear and precise contextual framework for building and spreading open knowledge. We wanted to avoid a glorified picture of MOOCs; as usual when innovations captivate the educational and global academic worlds, initial fever has given way to controversies that we did not want to leave unanswered.