Here's a breakdown of the phrase:
* Nau mai: This literally translates to "You come", and is a welcoming gesture to someone arriving.
* Haere mai: This means "Come here", and is a welcoming gesture to someone who is staying.
Together, "Nau mai, haere mai" expresses a warm welcome, both for the arrival and the stay.
You can also say "Tena koe" which means "Welcome" or "Greetings". This is a more formal greeting and can be used in any situation.