An Advance Parole is issued to an alien who is applying for but does not have permanent resident status, whereas a Re-entry Permit is issued to a permanent resident of the U.S.

On its face, an Advance Parole is a piece of paper with the holder's photo on it, whereas a Re-entry Permit looks similar to a passport. An Advance Parole functions like a visa to the U.S. while a Re-entry Permit functions, occasionally, like a passport.

In other words, an alien with an Advance Parole still needs a foreign passport to enter the U.S,. while a permanent resident with a Re-entry Permit does not need a foreign passport to get into the U.S. Another difference is the duration: An Advance Parole is valid for one year, whereas a Re-entry Permit is valid for two years.

For more information about Re-entry permit, please click the following topics:
Description
Attorney Fee and Filing Fee for Re-entry Permit
Documents and information needed to apply for a Re-entry Permit
Frequently Asked Questions about Re-entry Permit
Maintaining Legal Permanent Resident Status