There are a variety of visas available to travellers to Australia. The type of visa you should apply for depends on the length of your stay, your passport and the purpose of your visit.
eVisitor (subclass 651)
This is a free visa for multiple visits to Australia for tourism or business purposes for up to three months at a time within a 12-month period. This visa is available to passport holders from a number of European countries and it cannot be extended.
Electronic Travel Authority visa (subclass 601)
This visa allows you to visit Australia as many times as you want, for up to a year, and stay for three months each visit. This visa is available to passport holders from a number of countries and regions, who live outside Australia. There is no visa application charge for an ETA, however a $20 service charge applies for online applications only.
Visitor visa (subclass 600)
The Visitor visa is designed for people who are not eligible for the eVisitor or Electronic Travel Authority visa. This visa allows you to visit Australia, either for tourism or business purposes, for up to three, six or 12 months. The base application fee for this visa ranges from $135 to $340.
For more information visit the Australian Government Department of Immigration and Border Protection website homeaffairs.gov.au