If your parents are outside Australia
Parent (Migrant) visa (subclass 103)
This is a permanent visa for parents who have children living in Australia.
Contributory Parent (Migrant) visa (subclass 143)
This is a permanent visa for parents with children living in Australia. This visa costs more than the Parent visa but is generally processed faster.
Contributory Parent (Temporary) visa (subclass 173)
This is a temporary visa valid for two years. If you hold this visa you can then apply for the permanent Contributory Parent visa (subclass 143).
Contributory Parent (Migrant) visa (from subclass 173 to subclass 143)
This visa is for holders of a temporary Contributory Parent visa (subclass 173), who want to apply for a permanent Contributory Parent visa (subclass 143).