The Constitution is the birth certificate of a nation state. It is the basis of legal authority. All law is derived from the Constitution. The Constitution establishes a framework under which law is made and administered.
The Australian Constitution in the tradition of all liberal democratic Constitutions establishes the three organs of government —
The legislative organ in Australia is Parliament, consisting of the Queen, the House of Representatives and the Senate. The executive arm (commonly called the government) consists of the Queen in whom executive power is formally vested by section 61 of the Constitution. In practice, executive power at the apex is exercised by the Prime Minister and Cabinet who delegate many powers and functions to the public service. The High Court of Australia stands at the apex of the judicial system, with a descending order of courts at various levels. The powers of the Queen under the Constitution are generally exercised by her representative, the Governor General. The powers which the Constitution vests in the Queen and the Governor General are exercised in accordance with conventions. This means that in practice these powers are generally exercised by the Prime Minister, the Cabinet and the public service. But there are exceptional situations when reserve powers of the Crown are intended to be invoked. See LJM Cooray, Conventions, The Australian Constitution and the Future, Sydney (1979) chapter 2. The judicial arm consists of a hierarchy of courts.