Advance parole is an immigration document issued by the United States. It is not a re-entry permit; it is only issued to aliens without permanent residency

Permanent residency

Permanent residency refers to a person's visa status: the person is allowed to reside indefinitely within a country of which he or she is not a citizen. A person with such status is known as a permanent resident....

. Advance Parole is permission for certain aliens, who do not have a valid immigrant visa

Visa (document)

A visa is a document showing that a person is authorized to enter the territory for which it was issued, subject to permission of an immigration official at the time of actual entry. The authorization may be a document, but more commonly it is a stamp endorsed in the applicant's passport...

, to re-enter the United States after traveling abroad. Such aliens include those who have applied to adjust their status to that of permanent resident or to change non-immigrant status. Advance parole must be approved before the applicant leaves the United States, or any residency application will in general be denied. Travel outside of the United States may have severe consequences for aliens who have been unlawfully present even if they have obtained advance parole.

Who needs Advance Parole?

Aliens in the United States who have:

• an application for adjustment of status pending.
• been admitted as a refugee
  Refugee
  A refugee is a person who outside her country of origin or habitual residence because she has suffered persecution on account of race, religion, nationality, political opinion, or because she is a member of a persecuted 'social group'. Such a person may be referred to as an 'asylum seeker' until...
  
   or have been granted asylum.
• been granted benefits under the Family Unity Program.
• been granted Temporary Protected Status.
• an asylum application pending.
• an emergent personal or bona fide reason to travel temporarily abroad.

Note: Aliens holding valid H-1 (temporary worker in a specialty occupation) or L-1 (intra-company transferee) visas and their dependants in H-4 or L-2 status who have filed for adjustment of status do not have to file for advance parole as long as they maintain their non-immigrant status.

Who is not eligible for Advance Parole?

Aliens in the United States are not eligible for Advance Parole if they are:

• in the United States without a valid immigration status.
• an exchange alien subject to the foreign residence requirement.
• the beneficiary of a private bill.
• under removal proceedings.

How does one obtain advance parole?

To obtain advance parole, file USCIS Form I-131 (Application for Travel Document), complete with supporting documentation, photos and fee, at your local USCIS office or the Service Center having jurisdiction over your place of residence. After receiving USCIS Form I-131, read it carefully and note the documentation and photos that must be submitted. Detailed information is provided in the instructions. Further information on forms, filing fees, and fee waivers is available in Forms, Fees & Filing Locations.

Does Advance Parole guarantee admission into the United States?

Advance parole does not guarantee admission into the United States. Aliens who have obtained advance parole are still subject to the CBP inspection process at the port of entry.