Why did the British & Maori want a treaty?

WALT: understand why the Treaty of waitangi was created.

We have been learning about Waitangi day like when the pekaha people came 
to New Zealand and started trading with the Maori.

When I had done the scavenger hunt task I had to find information on a site that me teacher had created and answer all of them. 

An interesting fact about what happened in New Zealand long time ago was the the pekaha people taught the Maori how to read and write.