The visa you need for a backpacking holiday in Australia depends on how long you plan to stay. A holiday of less than three months requires only a tourist visa, also called an Electronic Travel Authority (subclass 601). This visa allows you to enter Australia as many times as you wish within a 12-month period, and stay for up to three months each time.
To stay longer than three months, you’ll need a different visa. A visitor visa, also called a Tourist Stream (subclass 600), is a temporary visa that can be granted for a stay of three, six or twelve months.
Neither a tourist visa nor a visitor visa allows you to work in Australia. If you’re looking to work during your holiday, consider applying for a Working Holiday Visa.