Parliamentary Vs. Presidential

In modern democratic countries, most regimes either follow a presidential or parliamentary form.

In a presidential regime, the principal character of the government is the Head of State (most often called the President) who is granted great political power by the Constitution and the legitimacy to use it from his popular election by universal suffrage. This President's power is balanced by a theoretically equally powerful elected representative body. As you probably figured, I just described the regime of the United States of America. It is the earliest and arguably the only truly presidential regime in the world, and every other constitution which seeks to create one is inspired from this wonderful document that is the Constitution of the United States of America.

In a parliamentary regime, the titular Head of State is a more or less powerless figure whose role is largely symbolic. This Head of State can be either a crowned head or a President who is elected by a political body and therefore has little popular legitimacy. The real political power, you guessed it, rests with the Parliament--for the purposes of this writeup, I will call the representative body Parliament, even though it may be called differently in different countries. The government emanates from and is dismissed by the representatives, and the executive power is not wielded by the Head of State, the President, but by the Head of the Government, the Prime Minister. The first parliamentary regime evolved out of the history of England and the United Kingdom. It was mimicked by all countries which had a regal legacy and wished to keep their crowned head even as they switched to democracy. It was also applied by many others simply because it's much easier to implement a parliamentary regime than a presidential one, which requires both separation and collaboration from the executive and legislative branches of the State.