After you are granted U.S. resident status, you could find yourself waiting many weeks or months to receive your green card. Until it arrives, the immigration authorities will place a temporary stamp (an "I-551 stamp") in your passport, which serves as temporary evidence of your permanent resident status. This stamp can be shown to employers or used to travel in and out of the United States. If the date stamp on the passport has expired before the actual green card arrives, you will need to visit your local USCIS office to get a current stamp. If you do not receive your card within a reasonable time, you should make an appointment with INFOPASS and visit USCIS to check its status.
Before your green card arrives, you will receive a letter from USCIS for ADIT processing. You will need to take the letter and your passport to a local USCIS office to provide the information that will be used on your green card.