This chapter presents a brief background to the development of research on flexible working. It examines the main approaches to flexible working, exploring the motivations behind the different approaches and the contexts in which they have emerged. The chapter aims to distinguish between the types of flexible working arrangements according to what is being changed and the way in which it is established. It introduces the contemporary debate in policy and practice circles about trying to match employer and employee needs under the banner of agile working and contrast this debate with wider perceptions of flexibility in workplaces. Despite its common usage, the term flexibility has been used in a number of different ways. These include flexibility in relation to the labour market, indicating an absence of regulation, organisational flexibility, or adaptability in response to change in the environment and flexibility relating to employment. The chapter also presents an overview of the key concepts discussed in this book.