A green card holder in the US is a permanent resident of the US and can live and work in the US permanently. However, after an extended absence, it is possible that a permanent resident may need to apply for permission to return to their home. To apply for this permission, you must file I-191 (Application for Advance Permission to Return to Unrelinquished Domicile). It is a good idea to file this form is you believe that there will be any problems with re-entering the US. For example, if you have been absent for some time and think you may not be readmitted, you may wish to speak with an immigration attorney and file Form I-191.