A 'Green Card' is known as PERMANENT RESIDENT CARD. What Is Permanent Residence? A person who has permanent residence status in the United States has the right to live and work in the US without restriction. This right may last for a lifetime, or it can be ended in some circumstances by an uninterrupted absence from the United States of more than a year or two. Permanent residents are said to have immigrant status in the US, in contrast to foreign nationals who are here temporarily in nonimmigrant status, such as F-1 students, J-1 scholars or H-1 temporary workers. In popular parlance, a permanent resident is said to have a "green card," an outdated reference to the permanent residence identification card, which used to be green but is now a pale red, white and blue. Permanent residents are also often said to have "PR." Permanent residence is not the same as citizenship. Permanent residents of the US remain nationals of their home country. They do not hold US passports and they do not owe allegiance to the US. They may not vote in elections and they may not hold elective office. After a certain period of physical presence in the US (five years in most cases, three in some), permanent residents can apply for US citizenship if they choose, but it is not necessary to become a citizen to retain the right of permanent residence Source: University of Pennsylvania http://www.upenn.edu/oip/iss/visa/permanent/index.html