Australia uses Australian dollars ($) and cents (c). The denominations are $100, $50, $20, $10, and $5 in notes and $2, $1, 50c, 20c, 10c, and 5c in coins.
You can change money at the airport or at most major banks. It's a good idea to know the exchange rate before you leave home. You can find this out from websites such as www.xe.com