This document discusses group dynamics related to sport performance. It covers the nature of groups and teams, Steiner's model of group performance, and factors that affect group cohesion and development. Specifically, it addresses Tuckman's model of group formation, which outlines the forming, storming, norming, and performing stages. It also discusses roles within groups, including formal, task-based, and informal roles. Finally, it defines group norms and how coaches can ensure players conform to norms to achieve positive impacts on team behavior and performance.