Your transit to some other country needs documentation like passport and visa. Passport is a single document issued by the country of your citizenship and is valid for travel to any part of the globe except to the countries, if any, specifically mentioned in the passport. Visa is an endorsement on your passport document that is made by the Consulate, Embassy or High Commission of the country where you intend to travel. Thus, a travel document is in two parts – passport and visa. A travel visa is a non-immigrant document and there are many different type of visas specified for various purposes of your travel. The application process and manner of issuing different visa types differ from country to country. However, a common visa, for instance, Schengen visa is available for some European Union countries under visa policy of the Schengen area.
Electronic Travel Authorization (ETA) or www eta immi gov au is a kind of registration, which is a visa alternative but not officially a visa and is needed for foreign travelers to a country that allows exemption from visa requirement under certain circumstances. These countries are Australia, Canada, United States, India, Sri Lanka, and Hong Kong. Some other countries have also made ETA rules for the foreign visitors to their country. ETA is very useful alternative to visa for short travel to a country that has this facility. If a traveler applies for visa and the same is rejected, the traveler has no recourse, but if ETA is rejected the traveler can opt to apply for visa.
Visa policy of Australian government is very liberal to allow visitors to enter in this country from many parts of the globe. Australia ETA policy allows visitor visa exemption to many different categories of travelers to enter in this country. However, there are many different kind of visas that are also available to visit this country.