New Zealand is the only country in the world with two official national anthems. Many countries have a "national" anthem and a "royal" anthem, but in NZ, "God Defend New Zealand" and "God Save the Queen/King" are co-anthems. In reality, "God Defend NZ" is much more commonly played as the national anthem.
The song was first performed in 1876; two years later, it was first translated into Maori, and the plethora of vowels in Maori is clear from the shorter length of the Maori version (as more vowels = more short syllables). The meaning of "Pacific's triple star" is still unclear; it could stand for a Maori symbol, for the Southern Cross or for the three largest islands in NZ, to quote three theories.
The anthem became official in 1976 after the presentation of a petition to the House. Today, the Maori first verse is typically sung before the English first verse. Full lyrics and a history are available from the government of NZ; the Maori lyrics and their English translation are here.
There are lots of videos online for this one; the NZ government site linked to above also has several mp3s.
This version is a video formerly played on an NZ TV station; it includes two verses in Maori and three in English.
The video below is NZ singer Hayley Westenra singing both "God Defend NZ" and "God Save the Queen" at a memorial dedication in Britain.