Firstly, an introduction as to how the Australian Parliament actually works.
The Australian Parliament has two houses. The House of Representatives has 150 members, and each represents an electorate. Each electorate has approximately the same number of enrolled voters in it, so the House of Representatives gives an approximately equal voice to each enrolled voter in the country. The count of electorates in Australia (and therefore the count of members of the House of Representatives) is based on population counts, and as a result periodically the Australian Electoral Commission must do a redistribution of the electorate boundaries when the population shifts have changed things enough. The last change in numbers was in 2001 when it went from 148 to 150 seats, while the last redistribution was in 2003 and resulted in South Australia losing one seat, Queensland gaining a seat, and Victoria kept the same number of seats but one seat was abolished while another new one was created.
The Senate has 76 members, with 12 members representing each of the 6 States (Western Australia, South Australia, Queensland, New South Wales, Victoria and Tasmania) with 2 members each representing the Australian Capital Territory and the Northern Territory. The Senate gives each State a theoretically equal voice.
Those numbers are governed by the Constitution of Australia. In the Constitution it states that each of the original six States of Australia must have have at least six Senate seats, and must be an equal number. Each of the original six States much have at least five seats in the House of Representatives, and the total number must be "as nearly as practicable, twice the number of Senators".
Bills (the things that get turned into the Laws of this Country) can be introduced by members of either house, except if is an appropriation bill (the bill is to do with proposing an expenditure or levying a tax). Appropriation bills can only be introduced by members of the House of Representatives.
The procedure to turn a Bill into Law is theoretically simple. The Bill is introduced into one of the two houses by the appropriate member. It is discussed, possibly amended, and eventually voted on. If it passes the vote, it is then sent to the other house for the same treatment. If it is amended in the other house, it must return to the first house for another round. Once the bill has been passed by both houses in exactly the same form (so no new amendments) it becomes law. The only variation to this is that in addition to not being allowed to be introduced into the Senate, appropriation bills can not be amended in the Senate either, only passed or rejected.
Theoretically, as the Queen's Representative, the Governor General can refuse to allow a bill to pass into law, but that power is nowadays nothing more than a formality.
The leader of the Country, the Prime Minister of Australia, is not directly elected. The PM is the leader of the Majority power in the House of Representatives. Currently, the Australian Labour Party holds 83 of the 150 seats in the House of Representatives, and therefore the Leader of the Party is the Prime Minister of Australia.