Australia and New Zealand are often lumped together when thought about around the world but the truth is that while they share some commonalities they are actually quite different countries. Their differences lie in their geography and their cultural identities.
In terms of culture, the biggest commonality between the two is the fact that they are both part of the British Commonwealth and have a long history with Great Britain. Australia was first discovered by Europeans in the 17th century and became a British colony in the 18th century. A portion of the island was set up as a penal colony. But the indigenous people of Australia lived there for thousands of years before European settlement. There are numerous different tribes and lineages, so they are often generally referred to as Aboriginals. They first came to the continent around 50,000 years ago, and they are believed to be the oldest continuing single culture still in existence on the entire planet. New Zealand, on the other hand, is a part of Polynesia, or a widespread group of islands in the south Pacific that were colonized in stages over time by a group of ethnic peoples called Polynesians. It was discovered by Europeans and colonized by the British around the same time as Australia, but its native population is completely different. The native New Zealanders are Polynesians called Maori. They first inhabited the islands around 1300 AD, crossing the ocean on long distance water canoes from other parts of Polynesia, likely Samoa and Tahiti.
In terms of geography, Autralia is a vastly larger land mass than New Zealand. But Australia is mostly desert land called the Outback that is very sparsely inhabited. The vast majority of the nation's population lives on the central and southern east coast, and there is another smaller popluation on the southern west coast. That is because these are the only two truly temperate areas on the entire island. The central desert and northernmost rainforests are less hospitable. This makes Australia as a whole one of the driest and flattest overall countries on Earth with one of the lowest population densities as well. New Zealand is made up of two main islands and numerous surrounding smaller islands. Although not originally formed by volcanic activity, New Zealand does experience much more seismic activity and the north island does have some mild volcanic activity which has enlarged it over time. New Zealand also has more forest landscape and denser foliage than Australia due to the lack of desert, and also more mountain terrain due to the seismic activity. The tallest point is Mount Cook at around 12,000 feet.