The Papal Archbasilica of St. John Lateran (Italian: Arcibasilica Papale di San Giovanni in Laterano), commonly known as St. John Lateran's Archbasilica, St. John Lateran's Basilica, and just The Lateran Basilica, is the cathedral church of the Diocese of Rome and the official ecclesiastical seat of the Bishop of Rome, who is the Pope.  

It is the oldest and ranks first among the four Papal Basilicas or major basilicas of Rome (having the cathedra of the Bishop of Rome). It claims the title of ecumenical mother church among Roman Catholics. The current archpriest is Agostino Vallini, Cardinal Vicar General for the Diocese of Rome. The President of the French Republic, currently François Hollande, is ex officio the "first and only honorary canon" of the basilica, a title held by the heads of the French state since King Henry IV of France.  

An inscription on the façade, Christo Salvatori, indicates the church's dedication to "Christ the Saviour", for the cathedrals of all patriarchs are dedicated to Christ himself. As the cathedral of the Bishop of Rome, it ranks above all other churches in the Catholic Church, including St. Peter's Basilica. For that reason, unlike all other Roman Basilicas, it holds the title of Archbasilica. 

The archbasilica is located outside of the boundaries of Vatican City proper, although within the city of Rome. However it enjoys extraterritorial status as one of the properties of the Holy See. This is also the case with several other buildings, following the resolution of the Roman Question with the signing of the Lateran Treaty.  

http://en.wikipedia.org/wiki/Archbasilica_of_St._John_Lateran