The Australian Constitution is the foundational legal document that outlines the structure and functions of the government of Australia. It was enacted on January 1, 1901, and established Australia as a federation of states, creating a system of government that includes a Parliament, an Executive, and a Judiciary. The Constitution also defines the powers and responsibilities of the federal and state governments. The document consists of a preamble and 128 sections, detailing various aspects such as the roles of the Governor-General, the process of law-making, and the rights of citizens. It can be amended, but changes require a national referendum, ensuring that any alterations reflect the will of the Australian people.