This document summarizes key concepts about group behavior from a chapter in an organizational behavior textbook. It defines groups and different types of groups, examines the five stages of group development and five properties of groups including roles, norms, status, size, and cohesiveness. It also discusses how norms and status can influence individual behavior within groups and contrasts the strengths and weaknesses of group decision-making versus individual decision-making. Finally, it evaluates evidence on cultural differences in groups and the effects of diversity on group performance and decision-making.