U.S. immigration laws govern the flow of foreigners coming across U.S. borders. They provide for criteria and procedures under which foreign nationals are permitted to come to the U.S. to reside, vacation, study or work. Based on the length of time foreigners are authorized to stay in the U.S., visas permitting them to enter the U.S. are categorized into immigrant visas or nonimmigrant visas, and their post-entry status in the U.S. is characterized as permanent or temporary status. Generally speaking, people who hold nonimmigrant visas come to the U.S. for temporary residence status, while those with immigrant visas are afforded lawful permanent residence status, commonly known as the green card status. Permanent residence may be obtained either by entering the U.S. with an immigrant visa issued by a U.S. consulate if a foreign national resides and applies for a visa in a foreign country or through adjustment of status if she is applying while in the U.S. Temporary residence is usually given to people who come to the U.S. with nonimmigrant visas for visiting family members, relatives and friends and touring the U.S. or for temporary employment. Like permanent residence, temporary residence may be gained by obtaining a nonimmigrant visa from a U.S. consulate if the foreign national lives and applies in a foreign country or by filing with the U.S. CIS an application for change of status if the person is in the U.S.