In addition, the Nuncio serves as the liaison between the Holy See and the Roman Catholic diocesan episcopate in the nation or region to which he is assigned. The national or regional episcopate is usually supervised by a national conference of bishops, whose presiding officer is often the highest ranking bishop or archbishop of that nation, or is elected from the diocesean ordinaries of the nation or region.
Formerly, the title Internuncio denoted a papal diplomatic representative of the second class, corresponding to Envoy Extraordinary and Minister Plenipotentiary as a title for diplomatic representatives of states (cf. Article 14, par. 2 of the 1961 Vienna Convention on Diplomatic Relations). Before 1829, internuncio was the title applied instead to the interim head of a mission when one Nuncio had left office and his replacement had not yet assumed it.
A legate a latere is a temporary papal representative or a representative for a special purpose.
Historically, the most important type of apocrisiary (a title also applying to representatives exchanged by a high prelate with a Patriarch) was the equivalent of a nuncio, sent by the Pope to the Byzantine Empire; during the fifth and sixth centuries, when much of Italy remained under Byzantine control, several Popes were former apocrisiaries.
Pro-Nuncio was a term used from 1965 to 1991 for a papal diplomatic representative of full ambassadorial rank accredited to a country that did not accord him precedence over other ambassadors and de jure deanship of the Diplomatic Corps in accordance with the Vienna Convention. In those countries, the papal representative's precedence within the corps is exactly on a par with that of the other members of ambassadorial rank, so that he becomes dean only on becoming the senior member of the corps.
For nations with whom the Holy See has no diplomatic ties, an Apostolic Delegate is sent to serve as a liaison with the Roman Catholic Church in that nation, though not accredited to the government of the state. Apostolic delegates have the same ecclesiastical rank as nuncios, but have no formal diplomatic status, though in some countries they have some diplomatic privileges. Indeed an apostolic delegate served as the Holy See's de facto diplomatic representative to the United States and the United Kingdom, until both major Anglo-Saxon states with a predominantly Protestant tradition established full-fledged relations with the Holy See in the late twentieth century, allowing for the appointment of a Papal Nuncio (see the list of British Ambassadors to the Holy See). Archbishop Pio Laghi, for example, was first apostolic delegate, then pro-nuncio, to the United States during the Jimmy Carter, Ronald Reagan, and George H. W. Bush presidencies.
Apostolic delegates are also sent to regions such as the West Indies and the islands of the Pacific. These delegates are also appointed nuncio to at least some of the many states covered by their delegation, but the area entrusted to them also contains one or more territories that either are not independent states or are states that do not have diplomatic relations with the Holy See.
In accordance with this article, many states (even not predominantly Catholic ones such as Germany and Switzerland and including the great majority in central and western Europe and in the Americas) give precedence to the Nuncio over other diplomatic representatives, according him the position of Dean of the Diplomatic Corps reserved in other countries for the longest-serving resident ambassador.
Botswana; Comoros; Mauritania; Somalia
Jerusalem and the Palestinian Authority; the Arabian Peninsula; Brunei; Laos; Malaysia; Myanmar/Burma; Viêt Nam (currently vacant)
the Antilles (Anguilla, Antigua and Barbuda, Aruba, Bahamas, Barbados, Belize, Bermuda, British Virgin Islands, Cayman Islands, Dominica, French Guyana, Grenada, Guadeloupe, Guyana, Jamaica, Martinique, Montserrat, Netherlands Antilles, Saint Kitts and Nevis, Saint Lucia, Suriname, Trinidad and Tobago, Turks and Caicos Islands, Saint Vincent and Grenadines)