In the most basic terms - to free the flow of goods from Canada, the US and Mexico allowing the 3 partners to sell stuff to each other without tariffs.

North America Free Trade Agreement: Tariff free trade of products between countries of North America.

NAFTA is a treaty between Canada, Mexico, and the United States that was designed to foster greater trade between the three countries. NAFTA has been in effect since 1 January 1994. It has since been updated with two major additions, the North American Agreement for Economic Cooperation (NAAEC) and the North American Agreement for Labor Cooperation (NAALC). A very recent addition was the Security and Prosperity Partnership of North America, designed to foster cooperation on issues of national security. One important thing that NAFTA did right away was to eliminate a large number of tariffs on goods shipped between the three countries. American goods, mostly, were being sold to Canada and especially to Mexico and carried with them a high tariff. Mexico and Canada did not wish to pay the tariffs, so the goods were not sold in North America. Prime examples of these goods were cars, car parts, computers, and food. As a result of NAFTA, Mexico especially has purchased goods from the US in much greater numbers than before. This saves Mexican companies money on imports, and it saves American companies money on export shipping costs. Canada has benefited in this way as well, although not nearly to the extent that Mexico has. I hope it is clear enough. Regards.

to contain miri's cuteness ;)

The first answer gave a clear definition, but it also had some bias and therefore did not give you the whole story. Yes it has beneficial for some, but also hurt others. Mexican corn farmers faced a 50% reduction in the price of corn when highly subsidized corn cam from the US into Mexico. There is vast opposition to NAFTA and other free trade agreements.

To have absolute control of the economy of both Canada and Mexico

To create a free trade area in North America.

It loosened to taxes between the USA, Mexico and Canada to encourage trading.