Australia Visitor Visa Guide & Assessment:

While visiting Australia, three kinds of Visas can be applied for. Your trip might be business oriented or recreational. The visit visa can be Electronic Travel Authority (subclass 601), Visitor Visa (subclass 600), Medical Treatment Visa (subclass 602), Transit Visa (subclass 771) or a eVisitor (subclass651).
The Australian visit visa cannot be applied by someone who is already in possession of Australian citizenship. Recreational and tourist visa includes activities like visiting friends and families, vacations, and holidays. Business visit or venture may include activities like setting up a business, exploring business possibilities or attending some professional conference or seminar.
The subclass 600 or the visitor visa is a comparatively long term visa as compared to other visit visas. The visa is issued from time periods of 3 to 6 or up to 12 months at a time. The visa is available for not only people outside Australia but also from inside of Australia. The visitor visa is available for recreational and business ventures.
The subclass 601 visa for Electronic Travel Authority is issued for recreation, tourism or business visits. Since it is tourism and business based visa it is available for a good few number of countries like Brunei, Canada, Honk Kong, Japan, Malaysia, Singapore, South Korea and United States. The visa is an electronically stored authority. The visit visas can be issued for up to a time period of three months.

In case of a visit for medical treatment, you should apply for the Medical treatment visa or the subclass 602.
The subclass 651 or eVisitor visa is again a visa issued or recreation or business. The visa is meant to be issued to passport holder from the countries of the European Union and other countries of the European continent. The visa is issued for up to duration of 3 months.
For travelling through Australia the transit visa can be applied for.