In the U.S., permanent residents who are not citizens are issued a permanent resident card, which is commonly known as a green card, to show that they are allowed in the country.
There are many ways for immigrants to obtain a green card and one of the most basic is by being the immediate relative of a U.S. citizen. Those who qualify to petition for such a green card include the citizen's spouse, unmarried children under 21 years old and parents, if the the citizen is over 21 years old.
Those who are an immediate relative of a U.S. citizen may file Form I-485, Application to Register Permanent Residence or Adjust Status to apply for permanent residence status if at the same time the citizen files Form I-130, Petition for Alien Relative. These forms can be filed while one is inside the U.S.
The U.S. Citizenship and Immigration Services gives special priority to the green card applications of immediate relatives of U.S. citizens. In addition, such green card applicants do not have to wait for a visa number because there is no limit on the number of visas for immediate family members.