The Trans-Pacific Partnership agreement at a glance

The Trans-Pacific Partnership has been crafted to encourage free trade and investment between 12 countries connected by the Pacific Ocean. Photo / NZME

The TPP has been hailed as the "biggest trade deal in a generation".

The TPP is a free trade agreement involving 12 nations connected by the Pacific Ocean.

The agreement is designed to free up trade and investment between the countries.

After years of controversy, mainly around the secrecy of the deal and the lack of public consultation, the document will be signed tomorrow at 11.30am.

The countries involved are New Zealand, Australia, Canada, United States, Mexico, Japan, Malaysia, Brunei, Vietnam, Singapore, Peru and Chile. At the signing tomorrow those countries will be represented by trade ministers or, in some cases, foreign ministers.

While it is a complex agreement, you should care about the deal because New Zealand is a small trading nation with a focus on exports. The deal will have an impact on our economy and relationships with international corporations and the other 11 countries.

In general, the trade deal is expected to increase the wealth of New Zealand by boosting exports into powerful economies.

A positive take from the agreement is an increase in opportunities for Kiwi businesses to sell their products to markets in the Pacific Rim countries without paying tariffs.

Some of the downsides include the idea the deal opens up the possibility of corporations suing the New Zealand Government if they feel the deal isn't being upheld.

People have raised the point that it diminishes New Zealand's sovereignty and challenges democracy.

It's worth remembering that every time a country signs an international agreement, whether it is based on trade or maintaining peace, its sovereignty diminishes.

At 11.30am tomorrow the document will be signed. The deal won't be ratified, or come into effect, until all the countries have gone through the process of voting on it, or passing it into law. That could take two years.