Hard to differentiate for foreigners but I'll attempt to explain the origins of Aussie sport a little bit.

This is a map of Australia and New Zealand.
Looking at the map either Rugby League or Union dominates the North-East Coast of Australia and New Zealand and Aussie Rules dominates the West, the Central North and the whole South of Australia.
West Australia, South Australia, the Northern Territory, Tasmania and Victoria are all aussie rules heartland and the ACT, New South Wales, Queensland and New Zealand are rugby heartland, in a lot of areas either Aussie Rules, Rugby League and Rugby Union are played exclusively as in it is unaccepted socially to play a different code

As an example of this I grew up playing Aussie Rules, Basketball, Cricket, Soccer and Squash but absolutely no rugby at all, in Queensland a person might grow up playing Ruby League or Union, Basketball, Cricket, Soccer and Surf but play no Aussie Rules at all.
Right now where I am sitting I can think of at least 20 Aussie Rules Clubs within a 20 kilometre radius and 1 rugby club, it would be the opposite in Queensland or New South Wales.
Rugby and Aussie Rules are our main winter sports and cricket is our national summer sport so all over Australia people will play rugby or football and then EVERYONE switches to cricket in summer.
The reason Aussie Rules was invented was so that cricketers could keep fit during winter and the rest is history.
Australia is a sports mad country and so is New Zealand, the rivalry between New Zealand and Australia exists mainly in sport over cricket and rugby and despite these sports the rivalry is overblown, there is a definite rivalry between the AFL and the NRL and ARU over territory but there is probably a bigger rivalry in rugby between the NRL and ARU which is ancient.
Queensland and New South Wales hate each other more over Rugby than any beef Australia and New Zealand could ever have.