This overview outlines key issues in learning with an open learner model (OLM). Originally, learner models remained hidden, as their primary role was to enable a system to personalize the educational interaction. Opening the model in an understandable form provides additional methods of prompting reflection, planning, and other metacognitive activities that are important in learning. Learner-system discussion, editing or other interaction about the learner model can allow users to contribute more directly to the modeling process to increase its accuracy, while at the same time, further facilitating reflection as they justify their viewpoints to themselves and the system. Social learning can be supported by opening learner models to peers, helping learners to gauge their relative progress, and effectively seek collaborators. OLMs can also provide useful information to others supporting the learning process, such as teachers and parents. OLMs are set to take an increasing role as new learning technologies develop.