Postal vote, plebiscite, opinion poll - which is it?

In a few weeks' time, papers to vote in the postal ballot on same-sex marriage will likely start arriving in mailboxes across the country. The government says the voluntary, non-binding vote will help gauge Australia's opinion on the issue, and whether parliament should vote on changing the law. But many sections of society say they face barriers to taking part.

Parliament House, Canberra Source: SBS