Liturgy is the public prayer and worship of the Church. The Greek origin of the word means "public work" or "service done on behalf of the people." In the Bible, liturgy is used in reference to the priests' duties in the Temple. In the Church today, liturgy is the official public worship of the Church and includes Mass, Sacraments, and the Liturgy of the Hours.

The Catechism of the Catholic Church teaches that, "it is the whole community, the Body of Christ united with its Head, that celebrates. 'Liturgical services are not private functions but are celebrations of the Church which is 'the sacrament of unity,' namely, the holy people united and organized under the authority of the bishops. Therefore, liturgical services pertain to the whole Body of the Church. They manifest it, and have effects upon it.'" (1140)