Green card is the name used by many people for permanent residency. Permanent residency is the right to live and work in the United States. A permanent resident may eventually become a US Citizen if he meets certain criteria. A permanent resident may lose his status if, for example, he commits a crime of moral turpitude, OR if he leaves the US for a period of more than one year without an advance permission to return. You must have grounds in order to apply for permanent residency.