‘What is public health?’ explains that public health is a very broad concept with changing or varying definitions over time and in different countries. In its narrowest sense, it refers to the health of a population, the longevity of individual members, and their freedom from disease, and in its widest sense it is concerned with the promotion of health and well-being. In 2005, the UK Faculty of Public Health grouped the ‘public health function’ into three areas: health improvement, health protection, and health service improvement. The lack of a clear definition for public health has led to criticism. Should public health focus on achievable technical solutions or aim at wider social change?