If you want to go on vacation to New Zealand or visit family and friends, you can do it by applying for a tourist/visitor visa. People from countries that are not exempt from visa need a visa in order to enter New Zealand.
If you have one of these nationalities you are exempt from a visa to New Zealand. See list of countries exempt from Tourist visa to New Zealand.
Nationals of these countries receive approval on entrance, which is in fact a 3 months visitor visa. In order to get a tourist visa to New Zealand you need to provide personal information and details about your planned stay in New Zealand.
The length of your visitor visa depends on the circumstances of your visit to New Zealand. For example, if you are a grandparent of a citizen or resident of New Zealand you can apply for a grandparent visa, which allows you to stay in New Zealand for a total of up to 18 months over a period of 3 years.