This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book addresses situations in which workers are exposed in the course of their employment to unnecessary risk as a result either of their personal circumstances or because of the circumstances in which their employer uses their services. This in turn may depend on the contractual agreement under which they are employed. The book concerns providing some contextual framework for the chapters that follow. It explains what is meant by the term vulnerable worker and the associated term, precarious work. It then, by way of illustration, reviews the literature on one particular area, namely the vulnerability of domestic workers, and uses it as a case study of vulnerable working. The development of domestic work within the home was initially considered a matter of family law and this classification was crucial for its exclusion from labour law.