The goal of this research was to understand the different kinds of learning that take place in Mod The Sims (MTS), an online Sims gaming community. The study aimed to explore users' experiences and to understand learning practices that are not commonly observed in formal educational settings. To achieve this goal, the researcher conducted a four-year virtual ethnographic study that followed guidelines set forth in Hine (2000). After Hine, the study focused on understanding the complexity of the relationships between technology and social interactions among people, with a particular emphasis on investigating how participants shaped both the culture and structure of the affinity space. The format for the dissertation consists of an introduction, three core chapters that present different sets of findings, and a concluding chapter. Each of the core chapters, which can stand alone as separate studies, applies different theoretical lenses and analytic methods and uses a separate data set. The data corpus includes hundreds of thread posts, member profiles, online interview data obtained through email and personal messaging (PM), numerous screenshots, field notes, and additional artifacts, such as college coursework shared by a participant. Chapter 2 examines thread posts to understand the social support system in MTS and the language learning practices of one member who was a non-English speaker. Chapter 3 analyzes thread posts from administrative staff and users in MTS to identify patterns of interactions, with the goal of ascertaining how users contribute to the ongoing design and redesign of the site. Chapter 4 investigates user-generated tutorials to understand the nature of these instructional texts and how they are adapted to an online context. The final chapter (Chapter 5) presents conclusions about how the analyses overall represent examples of participatory learning practices that expand our understanding of 21st century learning. Finally, the chapter offers theoretical and practical implications, reflections on lessons learned, and suggestions for future research.