Government is the institution through which a political unit, such as a country or an organization, exercises authority and sets rules. Government also controls and provides services for its people.

Governing an entire nation is a complicated task that requires the coordination of different institutions, departments, and individuals. Governments vary significantly, but they typically have a central authority, known as the head of state or the president, with a number of other officials that make up the executive branch, such as the secretary of state and the attorney general. The legislative branch makes laws. The judicial branch interprets laws and decides whether they are constitutional. The executive branch, which includes the president and his or her cabinet, carries out those laws. The judicial branch makes sure that the executive and legislative branches follow the law.

The central function of any government is to protect its citizens. This can include national security, but it also means protecting the health and safety of those citizens. Governments also provide goods that cannot be produced by the market, called public goods. Two important examples are education and healthcare. The market is not able to provide these items in large enough quantities and at low enough prices to satisfy everyone’s needs, so they must be provided by governments.

Almost every society has some form of government. Most have a local government that includes a school board or city council, as well as a county or state government. Some have a national government that provides a social safety net such as Social Security, Medicare and Medicaid.

Most people have more contact with their local and state government than they do with the federal government, but the federal government still has a lot of power. Governments at all levels set rules and laws, but they also fund many different things. For example, the federal government funds military spending, research in science and technology, and national parks. Local governments support schools, fire departments, police departments and libraries. They also handle tax collection and tax exemptions.

There are different types of government, such as democracies, monarchies and dictatorships. In a democracy, citizens choose the people who represent them. In a republic, a group of people elects a President and his or her cabinet. Governments also can be divided into branches, such as Congress, the Senate and the Supreme Court. The separation of powers ensures that one branch does not gain too much power over the others.

The principle of the separation of powers dates back to ancient times. The Greek statesman Polybius, for instance, described a mixed regime that had a monarchy, an aristocracy and a democracy. This led to the idea that a functional government should have three separate branches. This concept has been adapted by subsequent governments, such as the United States Constitution that calls for the President, Congress and the Supreme Court to act independently of each other. This system of checks and balances is a cornerstone of modern politics.