What is liturgy?
“Liturgy” comes from two Greek words meaning “the work of the people”, or “something that people do”. It means the worship of God in the broadest sense, not
just Mass. Boiled down to its essentials, all liturgy is a two-way action in which God speaks to his people, and we respond in prayer and worship.
Liturgy is not words in a book. In somewhat the same way that a piece of music is not the score and does not exist until someone performs it, so liturgy does not exist until the words on the printed page are given flesh in speech and singing, gestures and actions. The liturgist Aidan Kavanagh once famously said: “Liturgy ain’t liturgy unless it’s done.”
Quotes from Vatican II's document on the Sacred Liturgy
The liturgy is the summit toward which the activity of the Church is directed; at the same time it is the font from which all her power flows. For the aim and object of apostolic works is that all who are made sons of God by faith and baptism should come together to praise God in the midst of His Church, to take part in the sacrifice, and to eat the Lord's supper. The liturgy in its turn moves the faithful, filled with "the paschal sacraments," to be "one in holiness".
(Sacrosanctum Concilium, 10)
Mother Church earnestly desires that all the faithful should be led to that fully conscious, and active participation in liturgical celebrations which is demanded by the very nature of the liturgy. Such participation by the Christian people as "a chosen race, a royal priesthood, a holy nation, a redeemed people (1 Pet. 2:9; cf. 2:4-5), is their right and duty by reason of their baptism.
(Sacrosanctum Concilium, 14)