Today, Information and Communication Technology (ICT) has impact on every facet of our life including education, which has started an era of open online education. Massive Open Online Courses (MOOCs) are one of the major outcomes of open online education in the field of education. MOOCs have various dimensions, which open a wide scope for learning at different levels of education, i.e., school education, higher education, lifelong education and so on. MOOCs have potential to stand parallel to conventional education and existing distance education, and cater the different issues of conventional education and existing distance education because of their massive, open and online features. In the light of these issues, in the present paper, discussions are made mostly focusing on distance education as an alternative to conventional education; MOOCs as the alternative to conventional education and existing distance education; trend of growth of MOOCs; dimensions and scope of MOOCs; and learning environments of MOOCs. Towards the end of the paper some challenges of MOOCs are presented.