Parliamentary System

The parliamentary system is a type of government that the power to make and execute laws. This system has the characteristic of a no clear cut separation of power between the executive and legislative branches. This is the contrast of the presidential system. It is divided in two: head of government and the head of state. The parliamentary is distinguished by the head of government that depends on the direct or indirect support of the parliament. In the parliamentary a country is not ruled by different parties.
The head of government are the prime minister or premier. He or she the majority of the cases is the leader of the largest party in the legislature. In parliamentary systems the head of government is normally the leader of the largest party in the legislature. The Prime minister is the most senior minister of the cabinet.

The head of state may be a president or a hereditary monarch. The person in charge serves as the chief public representative of a monarchic or republican nation-state, federation, etc. The roles that they normally do are personifying the continuity and legitimacy of the state and exercising the political powers, functions and duties like being in charge of the constitution and its good use.

References
Ansers.com. 4 de Febrero de 2009 .
Answers.com. 04 de Febrero de 2009 .
Economicexpert.com. 4 de febrero de 2009 .
Wikipedia. 4 de Febrero de 2009 .