In most Westminster democratic systems - of which the UK parliament is the original, and convention in Australia follows closely, members of parliament are elected on the basis of a political party. The party system is much stronger in those countries that in the US, in many ways:
1) The party organization chooses who will stand for a particular seat as that party's representative in a process known as "preselection". This can be a combination of votes by paid up party members in local branches, with "head office" votes as well. By the way, in those countries, to be a member of a political party, you pay a membership fee and join a branch - and there may be an acceptance process. In the US, you simply say that you are a member of the democratic or republican party - and in some states, mark that preference when you enroll to vote.
2) Because there is no popular election for head of state / executive members, formation of government is done of the basis of which party can command a majority of votes on the floor of parliament. This is generally a no-brainer, but as we have seen in the last few weeks following the Australian federal election, can take a lot of negotiation. The party forming government determines who the Prime minister and other cabinet ministers are, and they can change their mind on who fills these positions at any time. The general population don't elect the Prime Minister directly.
3) Votes in both chambers are along party lines. If an individual member votes against the their party's policy, that is a big deal - known as "crossing the floor". The argument is that since you were elected as a member of the party, based on the party's platform, you support the party's vote.
4) There are some limited number of issues that are seen as having very personal implications - for example, abortion, matters affection religious beliefs, things like that. So the parties allow a "conscience vote" - where there is no binding party position, and each person may cast their vote according to their own beliefs.