Liturgy

 “From this it follows that every liturgical celebration,
because it is an action of Christ the priest
and of His Body which is the Church,
is a sacred action surpassing all others;
no other action of the Church can equal its efficacy
by the same title and to the same degree.”
Vatican II, Sacrosanctum Concilium (Constitution on the Sacred Liturgy), 7
 

The term “liturgy” comes from the Greek word, leitourgia, which means "public service”.  A more common word that is close in meaning to ‘liturgy’ is ‘worship’.  Worship is prayer, praise and worship directed towards God. The prime reason for our praise and thanksgiving is for the gift of our salvation in and through Christ.

But while worship can be a private act, liturgy is always a communal activity. Individual worship is best referred to as private prayer or devotion. It is not liturgy.

The people who do the work of liturgy, are the people of God, all the baptised - the Church. From Liturgy Brisbane, 2004, What is Liturgy?

Liturgy includes the celebration of Mass, the celebration of the Sacraments, and the Divine Office or Daily Prayer of the Church. The celebration of the Eucharist is the “source and summit” of our faith, and so all other liturgies flow from and to the celebration of Mass.