Abstract In this chapter, we outline the relationships between the three areas of health systems, health services, and inequalities in population health. We introduce the substantive question we address in this book: whether and how health systems influence inequalities in population health. We use a diagram to introduce the pathways that connect health systems and inequalities in population health, and the different levels at and between which they operate (Sect. 2.2). We use this diagram to organise the remaining chapters. We briefly introduce the social determinants of health in Sect. 2.3. The diagram in Sect. 2.2 is static; so, in Sect. 2.4, we briefly address feedback and change over time. We link this with the chapters to follow and end with a brief conclusion.