Short answers, pulled from the story.
A travel visa is a conditional authorization granted by a country to a foreigner to enter, remain within, or leave its territory. It is distinct from formal permission to enter: in most countries, a visa is subject to border control at the time of actual entry and can be revoked at any time, with the border officer making the final determination on admission.
As of 2019, the Henley and Partners passport index ranked the Japanese, Singaporean, and South Korean passports as having the most visa exemptions, each allowing holders to visit 189 countries without obtaining a visa in advance of arrival.
Svalbard is a Norwegian special territory that is an entirely visa-free zone under the terms of the Svalbard Treaty. It is the only territory of its kind, making it unique among all destinations globally.
A visa run is the practice of leaving a country just before the permitted stay expires, briefly crossing into a neighbouring country, and returning to receive a new entry stamp. Immigration authorities frown on the practice as a potential sign of illegal residency intent, and many countries have rules that prevent it from resetting the permitted stay. The United States, for example, does not grant a new period of stay to visitors returning from Canada, Mexico, or the Caribbean.
Countries that require exit visas for foreign workers include Iraq, Kuwait, Lebanon, Oman, Saudi Arabia, and the United Arab Emirates under the kafala system. North Korea requires exit visas for its own citizens. Uzbekistan abolished its exit visa requirement in 2019, following an explicit United Nations complaint. Cuba dropped its exit visa requirement in January 2013.
Passport-like documents date to 445 BCE in Persia and to the Han Dynasty in China. King Henry V of England formalized passports in 1414. After World War I, visas became essential for international travel. The League of Nations standardized passports in the 1920s, and the International Civil Aviation Organization took over regulation in 1947, leading to machine-readable and then biometric passports.