What it was
The Commonwealth of Australia was born in 1901 when six colonies united as a single nation. Under its constitution it is a federation, with power shared between the national government and the states.
Role
The federal government handles defence, foreign affairs, trade, and immigration, while the states run schooling, policing, and the like. Parliament has a House of Representatives and a Senate, and a prime minister leads the government.
Fate
Beginning as a self-governing dominion of Britain, the Commonwealth deepened its effective independence through the 20th century and today governs itself as an independent constitutional monarchy with the British monarch as symbolic head of state.