Catholic liturgy
The Catholic Church is fundamentally liturgical and sacramental in its public life of worship.
Liturgical principles
As explained in greater detail in the Catechism of the Catholic Church and its shorter Compendium, the liturgy is something that "the whole Christ", Head and Body, celebrates — Christ, the one High Priest, together with his Body, the Church in heaven and on earth. Involved in the heavenly liturgy are the angels and the saints of the Old Covenant and the New Covenant, in particular Mary, the Mother of God, the Apostles, the Martyrs and "a great multitude, which no man could number, out of every nation and of all tribes and peoples and tongues" (Revelation 7:9). The Church on earth, "a royal priesthood" (1 Peter 2:9), celebrates the liturgy in union with these: the baptized offering themselves as a spiritual sacrifice, the ordained ministers celebrating at the service of all the members of the Church in accordance with the order received, and bishops and priests acting in the person of Christ.