In its original meaning a 'public work" or service done in the manner of or on behalf of the people.  Through the liturgy Christ our High Priest continues the work of our redemption through the Church's celebration of the Paschal Mystery by which he accomplished our salvation. (Catechism of Catholic Church)

In the Liturgy, the Church at once expresses her faith and by God's grace deepens that faith.  In the Eucharist, Christ leads the community of the baptized to continual conversion to him, deeper communion with the Father, and to life in the Holy Spirit.  The Liturgy both enables and inspires the faithful to live the Christian faith: dedication to the teaching of the apostles, the communal life, the breaking of bread, and prayer. (National Directory of Catechesis)