Do you know what a vote is? It's when people decide on something by choosing between different options. Well, sometimes in Australia, there are big decisions that need to be made by a lot of people all at once. So instead of just having the leaders make the decision for everyone, they ask everyone to vote on it. This is called a referendum.
Referendums happen when the government wants to make a big change to the laws or the Constitution (which is like a rule book for the whole country). But before they can make that change, they need to make sure that most people in Australia actually want it. So they ask everyone to vote yes or no on the idea.
Whenever there's going to be a referendum, everyone in Australia gets a piece of paper in the mail that tell them what the referendum is about and what the different options are. Then they have to go to a special place to vote (usually a school or a community center) and tick the box for yes or no on the paper.
The government counts all the votes to see if most people said yes or no. If more people said yes than no, then they can make the change to the laws or the Constitution. If more people said no, then they can't make the change, and things stay the way they were before.
So that's what a referendum is like in Australia. It's like a big vote that everyone gets to take part in to decide on something really important.