The Visitor Visa (sometimes referred to as a Tourist Visa) is intended for people on a short-stay. If you come from a visa waver country you can fly to New Zealand and apply for a 3 month Visitor Visa at the border (6 months for citizens of the United Kingdom).
If you do not come from a visa waiver country or you have previously been declined a New Zealand visa, or removed or deported from any country you should apply for a Visitor Visa before you travel to New Zealand. If you try and come to New Zealand you may be refused boarding by the airline or be turned around upon arrival.
A visitor may stay in New Zealand for up to 9 months in any 18 month period or, in special circumstances, up to 12 months in any 24 month period. A Visitor Visa issued at the border can be renewed by making an application when you are in New Zealand.
A visitor may study in New Zealand for up to 12 weeks and may not work. Any Visitor Visa application must provide evidence that the applicant has at least $1,000 for personal maintenance for each month they intend to stay in New Zealand. This evidence may either be 6 months of past bank statements of financial sponsorship from a New Zealand citizen or resident or a New Zealand company or government entity.