What is green card?
Green card is a document that gives an immigrant certain immigration rights, sometimes conditionally. Although it introduces significant amount of responsibilities, such as obeying US laws and paying taxes, it grants a limited scope of privileges that US citizens enjoy.
The United States green card is a widely recognized, albeit informal, name for a U.S. lawful permanent residency immigration status.
The name "green card" was acquired because this alien registration document was printed on a green thick paper between 1946 and 1964; now, after 2010, the card also carries green color, but it is printed on plastic, has multiple levels of hologram and magnetic protection (see picture on the right).
Alien or Green Card Number
Getting a green card is only part of the process if one is to become a lawful permanent resident. The physical card will have a number associated with it, also known as "alien number", which will be associated with a file in government's database, which tracks all immigration related history, employment records, application documents, and contact information among other things. Having this Green Card or Alien Number is crucial for the government to track the applicant and keep the information up to date.
One can argue that this violates one's privacy. As we mentioned above, the green card does not give one the same rights as United States citizens get to enjoy. One of them is privacy.
Limited Scope of Rights vs. Citizenship
As mentioned previously, a permanent resident is not a U.S. citizen nor a U.S. national. He or she is considered an immigrant into the United States; he or she enjoys most freedoms, responsibilities and obligations of a citizen (including a right to freely travel to, live and work in the USA and pay taxes). However, green card holders are not allowed to vote in the U.S. elections or hold an elected state or federal government office.
Path to Citizenship
Most green cards afford an immigrant a path to citizenship. While securing employment-based green card can allow one to apply for citizenship within five years of being a permanent resident, family and marriage-based green card can allow for an accelerated process. It can allow one to sit down for a citizenship test within three years of becoming a green card holder. No wonder there is an opinion that the easiest path to immigrating to the United States lies through marriage.