A head of state (or chief of state) is the public persona that officially represents the national unity and legitimacy of a sovereign state. In developing the current Constitution of France (1958), former French president Charles de Gaulle said the head of state should embody "the spirit of the nation" (l'esprit de la nation). In some countries, typically those with parliamentary governments, the head of state is a ceremonial figurehead that does not actually guide day-to-day government activities and may not even be empowered to exercise any kind of political authority (e.g., Queen Elizabeth II in the United Kingdom). In other countries, the head of state is also the head of government, such as in the U.S., where the president is both a public figurehead and the actual highest ranking political leader who, in practice, oversees the executive branch.
Some academic writers discuss states and governments in terms of "models".
An independent nation state normally has a head of state, and determines the extent of its head's executive powers of government or formal representational functions. In terms, the head of a sovereign, independent state is usually identified as the person who, according to that state's constitution, is the reigning monarch, in the case of a monarchy, or the president, in the case of a republic.
Among the different state constitutions (fundamental laws) that establish different political systems, four major types of heads of state can be distinguished:
In parliamentary systems the head of state may be merely the nominal chief executive officer, heading the executive branch of the state, and possessing limited executive power. In reality, however, following a process of constitutional evolution, powers are usually only exercised by direction of a cabinet, presided over by a head of government who is answerable to the legislature. This accountability and legitimacy requires that someone be chosen who has a majority support in the legislature (or, at least, not a majority opposition - a subtle but important difference). It also gives the legislature the right to vote down the head of government and their cabinet, forcing it either to resign or seek a parliamentary dissolution. The executive branch is thus said to be responsible (or answerable) to the legislature, with the head of government and cabinet in turn accepting constitutional responsibility for offering constitutional advice to the head of state.