This course focuses on how social groups form, interact, and change. We look at the technical structures of social networks and explore how individual actions are combined to produce collective effects. This course introduces two conceptual models for how information flows is used in multi-person settings -- networks and games. Networks describe the structure of connections among people or documents. They permit mathematical analysis and meaningful visualizations that highlight different roles played by different people or documents, as well as features of the collection as a whole. Games describe the actions available to different people and how each person’s outcomes are contingent on the choices of others. They permit analysis of stable sets of choices by all players (equilibrium) and provide a framework for the analysis of the theoretical effects of alternative designs for markets and information elicitation mechanisms. The techniques learned in this course can provide a high level understanding of systems like Facebook, recommender systems used in sites such as Netflix, auction systems such as Ebay, and information networks used by search engines such as Google.