The Immigration and Nationality Act (INA) has been amended many times. When Congress enacts a law, it generally does not re-write the entire body of law, or even entire sections of a law, but instead adds to or changes specific words within a section. These changes are then reflected within the larger body of law.
The language changing the larger body of law is generally referred to as the "amendatory" language. Here you will find laws "amending" both the INA and the U.S. Code.