This chapter explains the diversity comes in many different forms and presents research findings on the advantages of diversity and the business case for diversity as well as the challenges of diversity. It discusses the suggestions for managing diversity based on best-known methods from diversity research. Diversity can be any difference between the members of a group on any given dimension. Diversity can be real, or it can be perceived by the members of the team. Relational demography theory represents some of the earliest work in the team diversity literature which examined the basic characteristics of teams. Diversity researchers sometimes describe diversity as a double-edged sword because diversity can be both helpful and challenging for organizations and teams. The way in which the organization's leadership approaches diversity is also important. The chapter also presents an overview of the key concepts discussed in this book.