This article elaborates a model for understanding pedagogy in online educational forums. The model identifies four key components. Intellectual engagement describes the foreground cognitive processes of collaborative learning. Communication processes operating in the background accumulate an ever richer store of shared understandings that enable the forward movement of the conversation. The collaborative process requires a moderator to coordinate communication and learning in a group. The moderator in online education is usually a teacher who shares knowledge in the process of leading discussion. Finally, a successful discussion generates intrinsic motivations to participate, which keep the discussion going. This framework is designed to bring out the complexity of online discussion and to provide a basis for advising teachers and evaluating applications and software. (Contains 2 figures and 1 table.)