The TN (NAFTA) visa is a non-immigrant status unique for Canadian and Mexican citizens. TN visa was created by virtue of the 1994 NAFTA treaty. It allows American, Canadian and Mexican citizens to work in each other's countries in certain professional occupations. Within the TN list of occupations, a Canadian or Mexican citizen can work in the USA for up to four years at a time.
However, the TN status may be renewed indefinitely in one to four-year increments. The TN it is not a permanent visa and if the US immigration officials suspect that it is being used as a de facto substitute for a Green Card they may refuse further renewals. Spouse and dependent children of a TN professional can be admitted into the United States under the TD status.
Main advantages of the TN visa over other US immigration visas: