Every diocese in the Catholic world has a cathedral it is the chief church of the diocese, the bishop's church. It is not uncommon to hear someone refer mistakenly to an especially large or magnificent church as a cathedral. But it isn't size or décor that matters, its the bishop. That said, there is one physical feature that sets a cathedral apart from all the other churches in the diocese: the bishop's throne, which is usually set on a raised platform within the sanctuary. The Latin word for a raised chair or throne, cathedra, is the source of out English word, cathedral.
Defining a basilica is a bit more complicated. Fundamentally a basilica is an architectural term for a certain style of building, and, as is often the case in Catholicism, the basilica comes to us from the Romans. When the ancient Romans spoke of a basilica they were referring to a large, high-ceilinged hall with three long aisles. The Romans used basilicas as courts, public meeting areas, and even as indoor markets an early form of our shopping malls. In the fourth century, after Emperor Constantine legalized Christianity, many bishops modelled their churches and cathedrals on the Roman basilica, setting up the altar at the far end of the hall.
The term basilica comes from a Greek word meaning regal or kingly, in other words, a cut above the rest. Over the centuries the Catholic Church has used basilica in this sense, with the pope granting the title Minor Basilica to a church that has unusual historical significance, or is especially sacred because of the presence of a relic or relics. There are over 1400 minor basilicas around the world, 527 just in Italy alone. These honorary basilicas include the great church at the grotto in Lourdes, the Cathedral of St Mark in Venice, the Shrine of Ste. Anne de Beaupré in Quebec, and the National Shrine of the Immaculate Conception in Washington, D.C. The designation Major Basilica is restricted to the four greatest churches in Rome St Peters, St John Lateran, St Mary Major, and St Paul-Outside-the-Walls.
While a cathedral and a basilica must meet certain criteria, just about anything can be a shrine. A box or chest that holds a precious relic is a shrine. The statue of St Francis in your backyard is a shrine. The replica of the Lourdes grotto behind the parish church is a shrine. The place where a saint was born or died, the site of a miracle or an apparition, these are all shrines, too.
Traditionally a shrine is a church that attracts pilgrims because it possesses an important relic or a wonderworking sacred image; examples of this type of shrine include the Shrine of St James the Greater in Compostela, Spain; the Shrine of the Holy House in Loreto, Italy; the Shrine of the Black Madonna in Jasna Gora, Poland. Over the last hundred years it has become popular to designate as a shrine a church that is a focus for a particular devotion, such as a perpetual novena to St Jude, St Anthony, or St Therese the Little Flower. By canon law, however, such an official designation must come from the local bishop.
Shrines have been part of Catholic life since the early days of the Church when Christians came to pray at the tombs of the martyrs. Statistics prove that shrines are still popular among the faithful: there are about 330 officially recognized shrines in the United States, approximately 970 in Latin America, and more than 6000 in Western Europe.
Source: Article written by Thomas J. Craughwell and published on catholiceducation.org