Public health is a scientific and practical endeavor. It aims at preventing disease and promoting health in a population. Public health has a specific way to use the concept of health. It is positive in the sense that it facilitates the measurement of the health status of a population over and above the absence of disease. Health in public health is a gradual, not an absolute, notion. Public health also targets health risks or health dispositions, which should not be confused with intrinsic health statuses. This chapter also discusses the aspect of referring to health within a population, which poses some issues of measurement. Finally, it is discussed what normative issues are due to the specific understanding of health in public health.