The Encyclopedia of Public Health was designed to offer the lay reader information about important aspects of the sciences, arts, practical skills, organization, essential functions, and historical traditions of the field. It is intended specifically for general readers with a high school or college level education, although many professional workers, trainees, and students of public health will find much here of use and interest to them.Public health is one of the essential institutions of society. It exists to promote, protect, preserve, and restore the good health of all die people, and it achieves these ends largely through collective action. The programs, services, organizations, and institutions devoted to public health are concerned with the health needs of entire populations. Professionals engaged in the field regard it as an organized effon directed at improving the health of populations by assuring the conditions in which people can be healthy. It thus differs from the healing arts such as medicine, dentistry, nursing, and pharmacy that aim their services at the health of individuals. Public health emphasizes health promotion, the prevention and early detection of disease, disability, and premature death. Many scientific disciplines, technologies, and practical skills are involved in public health, which can be viewed as a social institution, a collective discipline (one that focuses a large group of discrete disciplines on public health), and a practice.