If you are an Australian citizen and you wish to travel to New Zealand, you should know that you do not need a visa to cross the border. That is because both Australia and New Zealand are parts of the Trans-Tasman Arrangement.
According to the Trans-Tasman Arrangement, both Australians and Kiwis can travel to the other country without a visa. This applies not only when they wish to go on vacation, but an Australian citizen, for example, can go and work in New Zealand without a work visa. As you can imagine, the rule goes both ways.
At the same time, foreign people who hold permanent visa issues by one of the two states can travel from one to the other without a visa. All that is required is a passport. Again, this applies when they look for employment or education. It is safe to say that the Trans-Tasman Arrangement is quite similar to the European Union, where its citizens have freedom of movement and can go work in any country within the Union.
As for the other nationalities around the world, there are two categories of travelers. Those who come from a visa waiver country, and those who do not. As far as the first category is concerned, the people who travel to New Zealand need a visa, but only if the time period they wish to spend inside the country exceeds 3 months. However, British nationals are allowed to stay inside New Zealand for up to 6 months without a visa. For instance, if you are German, you can go to New Zealand without a visa. You only need a passport. But just if you do not plan to stay more than 3 months. If you want to remain for longer, you need to apply for a New Zealand visa.
The second category consists of people who do not originate from visa waiver countries. In this case, no matter how much you plan to stay in New Zealand, you need to apply for a visa. Lucky for you, you can apply online with iVisa.
The bottom line is that if you are an Australian citizen and you plan a vacation in New Zealand, you do not need a New Zealand visa. You can go there anytime you want, and stay for as long as you want. You can find employment or enroll in a public school system. There are some restrictions, of course, but those apply only in exceptional circumstances.