Liturgy is derived from the Latin word “liturgia,” meaning “a public work.” In the Christian context, the Liturgy is the Church’s participation in the “work of God”; a participation in the Paschal Mystery of Jesus Christ. The work of salvation, which the Old Testament is a prelude to, was accomplished through the Passion and Resurrection of Jesus. It is this salvific mystery that the Liturgy of the Church proclaims and celebrates so that the faithful may live from it and bear witness to it in the world.
 
The Liturgy is an exercise of the priestly office of Jesus Christ. “It involves the presentation of man’s sanctification under the guise of signs perceptible by the senses” (Sacrosanctum Concilium 2). The full public worship of the Church is offered by the Mystical Body of Christ, with Jesus as the Head, and is a sacred action that surpasses all others. As a result, its function is twofold: to give honor and praise to God (worship), and to obtain blessings for mankind (sanctification). In the end, the Liturgy is both the font and summit of the Church.  It is in the sacraments, especially the Blessed Eucharist, that Christ works in fullness for the transformation of all.

As Pope Emeritus Benedict said:
"The liturgy is never a mere meeting of a group of people, who make up their own form of celebration and then, so far as possible, celebrate it themselves. Instead of that, through our sharing in Jesus’ appearing before the Father, we stand both as members of the worldwide community of the whole Church and also of the communion sanctorum, the communion of all saints, Yes, in a certain sense this is the liturgy of heaven. That is its true greatness, that heaven is torn open here, and we are incorporated in the great chorus of praise. And that is why the Preface ends with these words: With all the choir of angels in heaven, we join in singing. And we know that we are not alone, that we are joining in, that the barrier between earth and heaven has truly been torn open." (God and the World)