Tapu is the strongest force in Māori life. It has numerous meanings and references. Tapu can be interpreted as "sacred", or defined as "spiritual restriction" or "implied prohibition", containing a strong imposition of rules and prohibitions. A person, an object or a place, which is tapu, may not be touched by human contact. In some cases, not even approached. A person, object or a place could be made sacred by tapu for a certain time, and the two main types of tapu were private and public. Private tapu concerned individuals, and public tapu concerned communities.
In earlier times, tribal members of a higher rank would not touch objects which belonged to members of a lower rank. This was considered "pollution". Similarly, persons of a lower rank could not touch the belongings of a highborn person. Death was the penalty.
A breach of "tapu" was to commit a hara (violation) could incur the wrath of the Gods. Certain objects were particularly tapu, so much so that it was a dangerous act to even touch them, apart from suitably qualified priests. In 1772 the French explorer Marion du Fresne was killed for breaching a particular "tapu".
In earlier times food cooked for a chief was tapu, and could not be eaten by an inferior. A chief's house was tapu, and even the chief could not eat food in the interior of his house. A woman could not enter a chief's house unless a special religious ceremony was performed. (the karakia)
An ariki (chief) and a tohunga (healer or priest) were lifelong tapu persons. Not only were their houses tapu but also their possessions, including their clothing. Burying grounds (urupa) and places of death (wahi tapu) were always tapu, and these areas were often surrounded by a protective fence.
Two other types of tapu were "rahui and "aukati", but "tapu" itself was the most powerful, the most important, and the most far reaching into Māori life.
"Noa", on the other hand, lifts the "tapu" from the person or the object. "Noa" is similar to a blessing. Tapu and noa remain part of Māori culture today, although persons today are not subject to the same tapu as that of previous times. A new house today, for example, may have a "noa" ceremony to remove the "tapu", in order to make the home safe before the family moves in.
Today, tapu observances are still in evidence concerning sickness, death, and burial. Tapu is also evident in the Marae and in the Whare. The original reasons for some "tapu" are unclear today, but other reasons for "tapu" included the conservation of natural environment. This was seen to benefit the community as a whole.
http://history-nz.org/maori3.html