Commitment
Same Sex
Thanks to John Howard and Julia Gillard, marriage is not an option for same sex couples. In order to publicly express their commitment to each other a commitment ceremony can be undertaken. However, although it can look and feel like a wedding ceremony it does not use the words prescribed by law and it is not recognised as a legal marriage.
Heterosexual couples
Fortunately you don't need to be a same sex couple to have a commitment ceremony.