A visa is a conditional authorization granted by a polity to a foreigner that allows them to enter, remain within, or leave its territory. Visas typically include limits on the duration of the foreigner's stay, areas within the country they may enter, the dates they may enter, the number of permitted visits, or if the individual can work in the country in question. Visas are associated with the request for permission to enter a territory and thus are, in most countries, distinct from actual formal permission for an alien to enter and remain in the country. In each instance, a visa is subject to entry permission by an immigration official at the time of actual entry and can be revoked at any time. Visa evidence most commonly takes the form of a sticker endorsed in the applicant's passport or other travel document but may also exist electronically. Some countries no longer issue physical visa evidence, instead recording details only in immigration databases.
A United States visa issued in 2014
Passport receipt for visa application, Embassy of Myanmar, Bangkok
Tourist entry visa to the People's Republic of China
Transit visa, issued by Japanese Consul Chiune Sugihara in Lithuania to Susan Bluman in World War II
In law, an alien is any person who is not a citizen or a national of a specific country, although definitions and terminology differ to some degree depending upon the continent or region. More generally, however, the term "alien" is perceived as synonymous with foreign national.
World War II poster
People of various background became naturalized at Kennedy Space Center in Florida (2010). Before the naturalization they were lawfully admitted permanent resident aliens.