An alien registration card is the official name for the identification card given to lawful permanent residents by the USCIS to identify them as such. Other names for the alien registration card include green card, permanent resident card, and...
green card
(Wex page)
A lawful permanent resident is a non-citizen who has been granted authorization to live and work in the United States on a permanent basis. As proof of that status, a person is granted a permanent resident card, commonly called a "green card."
...