You were probably granted a Conditional Green Card. A Conditional Green Card is a green that is valid for only two years. After two years, the Conditional Green Card holder must file a Petition to Remove his Conditional Residency in the United States and become a Permanent Resident of the United States. The USCIS is granting Conditional Green Cards to people who at the time of their Green Card Marriage Interview are married for less than two years. The Conditional Green Card is a process that the USCIS is using in order for them to have a second chance to check the validity of the marriage.