A hongi is a traditional Māori greeting in New Zealand. It is done by pressing one's nose and forehead (at the same time) to another person at an encounter.
It is used at traditional meetings among Māori people and on major ceremonies and serves a similar purpose to a formal handshake in modern western culture, and indeed a hongi is often used in conjunction with one.
In the hongi, the ha (or breath of life), is exchanged and intermingled. The breath of life can also be interpreted as the sharing of both party's souls.