An immigrant is a foreign national who is authorized to live and work permanently in the United States. You must go through a multi-step process to become an immigrant based on employment:
The United States Citizenship and Immigration Service (USICS) must approve an immigrant petition (application) that was filed for you, usually by an employer.
In most employment, a U.S. employer must complete a labor certification request (ETA 750) for you from the Department of Labor’s Employment and Training Administration.
The State Department must give you an immigrant visa number, even if you are already in the United States.
If you are already in the United States, you must apply to adjust to permanent resident status when a visa number becomes available.