What do the terms “Holy See“, “Vatican“, and “Catholic Church” mean? Don’t they all refer to the same thing? Aren’t they basically interchangeable?
No, they refer to three distinct but not separate concepts.
The term “Holy See” (also called the “Apostolic See”) dates from ancient times and refers to the Pope and his closest collaborators; in other words, it refers to the central governing structure of the Catholic Church (Pope, Secretary of State, Roman Curia). The Holy See is a subject (party) of international law: it can enter into accords and other agreements and relationships with nation-states and non-governmental organizations. Thus the Holy See has long been involved in diplomatic activity, and the Church has its own academy for ecclesiastical diplomats. These diplomats, acting in the name of the Pope, represent the Church before governments throughout the world in order to protect and defend the rights of Catholics and also to promote values that are common to all (or almost all), such as peace. Our Apostolic Nuncio in Washington (papal diplomat to the United States) is Archbishop Carlo Viganò.
The Vatican, properly called “Vatican City State“, is a very recent reality; it is the sovereign territory of the Holy See. Vatican City State was created as a result of the Lateran Pact of 1929, when the Holy See and Italy signed an agreement that restored a small sliver of territory to the Holy See, along with several extraterritorial parcels. (Up until 1870 large parts of what is now Italy were known as the “Papal States” and were under the direct control of the Pope. So until that point the Holy See had had a sovereign territory – much larger than it does now – that over the centuries changed according to political fortunes and so forth. From 1870 until 1929 the Holy See did not have a territory of its own, properly speaking.) The name of the city-state comes from where it is located: it is built upon Rome’s Vatican Hill.
So until this point we see that the Holy See is a concept directly tied in with the Pope; Vatican City State is the territory of the Holy See. Neither one of these is synonymous with “Catholic Church”, though they are certainly both important aspects of the Church.
When we speak of “Catholic Church“, then, we are speaking about the Body of Christ, the body of the baptized faithful, who are spread all throughout the world. The Church is especially present where the Eucharist is, but she is also present in each one of the faithful, who are the “living stones” that make up the great Church that has gone to and must continue to go to all nations.
In many news reports nowadays you will see very imprecise use of the above terms, especially when it comes to the Vatican: many articles give the impression that the word “Vatican” is a nickname for some rogue who sits in an office in Rome issuing outrageous decrees all day. It’s fine if we use “Vatican” as a sort of catch-all in some contexts, but sometimes we also need to be more precise. For example, it’s one thing for the Pope to issue a decree about something of importance. It’s quite another thing if a lower-level Vatican office issues a decree about some matter. The weight of authority is simply not the same.
So, while many journalists cite “Vatican sources”, for all we know they might have interviewed one of the janitors who works in an obscure corner of Vatican City State! It’s best if we use the word “Vatican”, then, with reference to the sovereign territory of the Holy See, and not to individuals or groups of people who work there.
Hopefully this helps to clear up a bit of confusion on these terms, though far more could be said about each one!