A type of
political system which has the
legislature and the
executive in the same institution.
For example, in the UK the Prime Minister is a member of the House of Commons and also the head of the government.
This is unlike the USA's model where the executive (The President) is seperate from the legislature (the House of Representatives and the Senate). This sort of model is called a presidential system.
The parliamentary system has benefits over the presidential system (as well having some problems). The main benfit is that action can be taken very quickly and legislation is passed quickly and much more easily than in the presidential system.
However, there is an issue over the undemocratic nature of the parliamentary system since the Prime Minister has the ability to become an elected dictator and, theoretically, take over power from the rest of government.