The Constitution Act 1901 is the foundational legal document that established the Commonwealth of Australia. It came into effect on January 1, 1901, marking the unification of six separate British colonies into a single nation. The Act outlines the structure of the government, including the roles of the Parliament, Executive, and Judiciary, and sets forth the powers and responsibilities of each. The Constitution also includes provisions for the rights of the states and the federal government, ensuring a balance of power. It has been amended several times to reflect changing societal values and needs, but its core principles remain intact, guiding Australia's governance today.