I quote the Wikipedia:"The Papal Basilica of Saint Mary Major (Italian: Basilica Papale di Santa Maria Maggiore, Latin: Basilica Sanctae Mariae Majoris ad Nives[1][2]), is an ancient Roman Catholic Marian basilica of Rome. It is one of the four major or four papal basilicas,[3] which, together with St. Lawrence outside the Walls, were formerly referred to as the five "patriarchal basilicas" of Rome [4], associated with the five ancient patriarchal sees of Christendom (see Pentarchy). The other three papal or major basilicas are St. John Lateran, St. Peter and St. Paul outside the Walls. The Liberian Basilica (another title for the church) is one of the tituli, presided over by a patron—in this case Pope Liberius—that housed the major congregations of early Christians in Rome. Santa Maria Maggiore is the only Roman basilica that retained the core of its original structure, left intact despite several additional construction projects and damage from the earthquake of 1348.

The name of the church reflects two ideas of greatness ("major"), that of a major (or papal) basilica and that of the largest (major) church in Rome dedicated to the Blessed Virgin Mary.