Holy See
Although the Holy See is sometimes metonymically referred to as the "Vatican", the Vatican City State was distinctively established with the Lateran Treaty (1929) between the Holy See and Italy to ensure the temporal, diplomatic, and spiritual independence of the Papacy. As such, ambassadors are officially accredited to the Holy See and not the Vatican City State. Conversely, Papal nuncios to states and international organisations are recognised as representing the Holy See and the integrity of the Catholic Church along with its 1.3 billion members, not the Vatican City State, as prescribed also in the Canon law of the Catholic Church (1983). The "Holy See" thus refers to the See of Rome viewed as the central government of the Catholic Church. The Catholic Church, in turn, is the largest non-government provider of education and health care in the world, while the diplomatic status of the Holy See facilitates the access of its vast international network of charities.
Foreign relations of the Holy See
The Holy See, as a non-state sovereign entity and full subject of international law, started establishing diplomatic relations with sovereign states in the 15th century. It had the territory of the States of the Church under its direct sovereign rule since centuries before that time. Currently it has the territory of the State of the Vatican City under its direct sovereign rule. In the period of 1870-1929 between the annexation of Rome by the Kingdom of Italy and the ratification of the Lateran Treaty establishing the current Vatican City State, the Holy See was devoid of territory. In this period some states suspended their diplomatic relations, but others retained them (or established such relations for the first time or reestablished them after a break), so that the number of states that did have diplomatic relations with the Holy See almost doubled (from 16 to 27) in the period between 1871 and 1929.