If you are interested to apply for a green card (permanent residence) while that you have a permanent job offer in the United States, or if you are an employee and your employer is willing to sponsor a green card for you based on permanent employment in the United States, you may obtain the green card through the employment.
Unless you are eligible to petition for yourself (EB-2 National Interest Waiver, or EB-1A Extraordinary Ability), most employment petitions require a job offer and require that the employer petition for the worker. 140,000 persons are permitted to become green card holders through the following employment-based (EB) preference categories each year:
First: (1) persons of extraordinary ability, (2) outstanding professors and researchers and (3) executives and managers of multinational employers. 28.6% of the worldwide employment-based preference level, plus any numbers not required for fourth and fifth preferences.
Second: (1) persons of exceptional ability and (2) persons whose jobs require an advanced degree or its equivalent. National Interest Waiver is this EB-2 category. 28.6% of the worldwide employment-based preference level, plus any numbers not required by first preference.
Third: (1) professionals, (2) skilled workers and (3) unskilled workers. 28.6% of the worldwide level, plus any numbers not required by first and second preferences, not more than 10,000 of which to "*Other Workers".
Fourth: (1) religious workers and (2) other “special immigrants”: 7.1% of the worldwide level.
Fifth: investors with employment creation: 7.1% of the worldwide level, not less than 3,000 of which reserved for investors in a targeted rural or high-unemployment area, and 3,000 set aside for investors in regional centers by Sec. 610 of Pub. L. 102-395.
Persons in the EB-2 (except National Interest Waiver) and EB-3 categories are required to undergo the PERM process in order to obtain green cards through employment supported from their employees. Persons in the EB-1, EB-4 and EB-5 categories are never required to use PERM in order to qualify for green cards.
If you are living inside the United States, you can become a permanent resident through adjustment of status. Once the I-140, Immigrant Petition for Alien Worker, is approved and a visa number is available, you can apply on Form I-485, Application to Register Permanent Residence or Adjust Status, to USCIS to become a permanent resident.
You can become a permanent resident through consular processing if you are living outside the United States. Consular processing is when USCIS works with the Department of State to issue a visa on an approved Form I-140 petition when a visa is available.