The term "numerical limitations" means several things:

- First, it refers to the overall limits set by Congress on immigrants.

- Second, it involves the use of per-country caps.

- Third, and most important, numerically limited visas are organized along a system of preferences that favors certain aliens over others. Every immigrant wants the best shot at a visa, but qualifying for the easiest category - visas not subject to numerical limitation - is very difficult. Congress has reserved this category for immediate relatives of U.S. citizens, resident aliens returning from temporary visits abroad, and former U.S. citizens. Consequently, for the vast majority of aliens who want to immigrate, demand is much higher than the relatively short supply prescribed by law.