A cathedral is above all a church. Cathedrals are built for men to come and meet God, and to come together during celebrations or for personal prayer. That is the role of Notre-Dame de Paris, which calls people to peace and to prayer. In the cathedral, several masses are celebrated each day, especially on Sunday, the Day of the Lord, when thousands of worshippers from all over the world come together there. But Notre-Dame is also a cathedral: this church is where the archbishop of Paris, Monsignor André Vingt-Trois, has his seat, called a cathedra. Notre-Dame is also the mother church of all the residents of Paris. It is where all the believers from the Paris diocese come together for major celebrations like ordinations of new priests every year in June and processions for the Feast of the Virgin on 15 August, the day of the Assumption.