This document provides an overview of connectivist MOOCs (cMOOCs) based on lessons learned from running cMOOCs. It defines key concepts like open learning, connectivism, and cMOOCs. Some key points made are: cMOOCs are based on connectivist principles where learning is a process of connecting information sources and diversity of opinions; they require nurturing connections to facilitate continual learning; and assessing learning in cMOOCs can be challenging given their open and connection-based nature. The document shares lessons learned from running previous cMOOCs on needing critical mass of participation and exploring new tools like ePortfolios for assessment.