Public affairs encompass the idea of the relationship between institutions like government and corporations and the public which is affected by their policies and decisions. Public affairs are divided into two branches, public policy and public administration. Public policy is the action taken by administrative or executive branches of the government in a way that is consistent with institutional customs and the law. Public relations, lobbying, community involvement and grassroots politics all fall under the umbrella of public affairs.
Public administration is the implementation of government policies as done by civil servants, and also refers to the training and preparations of these civil servants. Public affairs generally include forms of government and branches of government, as well as security issues ranging from crime and criminal justice to the military and civil defense. It also involves preparation for emergency situations both on a large scale and within communities. Public affairs also include dealing with such issues as public health, environmental issues such as pollution, and industrial policies. Taxes, tariffs, and the regulation or deregulation of trade also fall under the umbrella of public affairs.
Politics are the process by which groups of people make collective decisions, specifically those involving governmental affairs. Today the term is used to describe the functions of various governments and the relationship of the government to the people it governs. The literal translation of politics from the Greek word means "of, for, or relating to citizens," which gives a sense of what ideally the role of a government is. Politics includes the regulations of public affairs and the methods used to create and apply government policies. Several different types of government, or States, have arisen over the years--monarchies, oligarchies, democracies, and many others.
Almost all governments today rely upon a constitution, which is a written (and in some cases unwritten) document which delineates the powers of the government and the writes of the people. The U.S. Constitution does this for the U.S., and has been changed over the years both by formal amendments and in the way that it is interpreted. Most modern governments are divided into branches of government, which handle specific responsibilities. In the U.S., the Federal government comprises the executive, judiciary, and legislative branches.