Whether you can enter New Zealand without a visa depends on your nationality. Many passport holders can currently enter for periods of up to 90 days visa-free (including citizens of the United States, all European Union member states, Canada, Brazil, Argentina, and Japan). UK passport holders can enter for up to six months without a visa and Australians can enter indefinitely.
However, from July 2019, the new eTA Zealand Electronic Travel Authorization will be implemented for all of the 60 visa exempt countries. Pre-registering an eTA application online will become obligatory for these citizens from October 1st, 2019.
The only exception will be citizens of Australia, who will continue to be allowed visa-exempt travel to New Zealand. However, Australian permanent residents will also be required to apply for the eTA (but not to pay the associated International Visitor Conservation and Tourism Levy.)