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.
Monarchies in Europe
Differently from the Holy See, in existence for almost two thousand years, the Vatican City was not a sovereign state until the 20th century. In the 19th century the annexation of the Papal States by the Kingdom of Sardinia, and the subsequent establishment of the Kingdom of Italy, was not recognized by the Vatican. However, by the Lateran treaty of 1929, the Kingdom of Italy recognized Vatican City as an independent state, and "vice versa". Since then, the elected monarch of the Vatican City state has been the current pope. The pope still officially carries the title "King of the Ecclesiastical State" (in Latin: Rex Status Ecclesiæ).