What is a bishop? I suspect most Catholics know the bishop appoints Parish Priests ("Pastors"), administers the sacrament of Confirmation, and wears a "pointy hat"! But, liturgically speaking, what is a bishop?
To answer this question, we first look at the Levitical priesthood of Aaron (the priestly brother of prophetic Moses the Lawgiver) in the Old Covenant. Now, don't get lost here; just remember there was always (A.) a High Priest, (B.) priests and (C.) other "Levites" in Israel's worship of God's Presence above the Ark of the Covenant.
In the Church of the New Covenant, this order remains, with the (A.) bishops as "High Priests", (B.) presbyters/elders/priests as "priests", and (C.) deacons as "Levites".
Every celebration of the Sacred Liturgy, especially of the Holy Mass, is a work of the bishop with the assistance of his clergy (priests and deacons) and the faithful. Even in his absence, the Mass, sacraments, daily Office, blessings and exorcisms are the work of the bishop celebrated in relation to him, for Christ the High Priest works through the bishops in the Sacred Liturgy.
So important is the bishop that even the word "church" applied to a community of Christians requires a relationship with a bishop. It is for this reason that we can speak of Orthodox communities as "churches", despite their separation from Rome, while "sons of the Reformation" do not belong to "church" communities (some call their leaders "bishops", but these Protestant leaders lack valid ordination).
Therefore, numbers 41 through 46 of the Constitution on the Sacred Liturgy says the clergy and faithful must foster the relationship to the local bishop in the Sacred Liturgy, while the bishop must foster the liturgical life of his diocese.
What is a bishop?
What is the liturgical relationship between a parish and the local bishop?
How can this relationship be strengthened?
How is this relationship sometimes harmed?