Interesting question Liliana. Although most bills are introduced into the House of Representatives and then sent to the Senate, bills may also be introduced in the Senate (except for money and taxation bills) and then sent to the House of Representatives. A bill is passed by either chamber on a majority vote. This means a majority (half plus one) of members or senators present vote to pass the bill in either a vote on the voices or division. Not all members or senators need to vote for the bill to be passed. The bill must be agreed to in identical form by both chambers, and given Royal Assent by the Governor-General for it to become a law.
Want more information about the lawmaking process? Check out this fact sheet.