A visa is a conditional authorization granted by a country to a noncitizen to enter and temporarily remain within that country. Visas typically include limits on the duration of the noncitizen's stay, territory within the country they may enter, the dates they may enter, or the number of permitted visits. Visas are associated with the request for permission to enter a country and thus are, in some countries, distinct from actual formal permission for an alien to enter and remain in the country. In each instance, a visa is subject to permission by an immigration official at the time of actual entry and can be revoked at any time.
A visa is commonly a stamp endorsed in the applicant's passport or other travel document. The visa, when required, was historically granted by an immigration official on a visitor's arrival at the frontiers of a country, but increasingly today a traveller wishing to enter another country must apply in advance for a visa, sometimes in person at a consular office, by mail or over the internet. The actual visa may still be an endorsement in the passport or may take the form of a document or an electronic record of the authorisation, which the applicant can print before leaving home and produce on entry to the host country. Some countries do not require visas for short visits.
Some countries require that their citizens, as well as foreign travelers, obtain an "exit visa" to be allowed to leave the country.