Marriage, according to law in Australia, is the union of a man and a woman to the exclusion of all others.
For now, same sex marriage is not legal in Australia and same sex couples who would like to celebrate their union can do so through having a Commitment Ceremony, but not a legal marriage. I have conducted several Commitment Ceremonies with same sex couples and can honestly say that, aside from the fact that they are not legally recognized in Australia, they pretty much look and feel like marriage unions. (see example of Commitment Ceremony Click here to download Commitment Ceremony).
If marriage between same sex couples becomes legal in Australia, and many think this is a real possibility in the not too distant future, then same sex couples may wish to plan for such an event.
See Same Sex Marriages Links & Downloads that presents examples of the debate why marriage equality matters but it must be emphasized that while this debate continues in Australia, marriages in Australia are still only legal between a man and a woman.