There are three orders of clergy that comprise the hierarchy of the Church. From the bottom up they are Deacon, Priest, and Bishop (i.e., they belong to the diaconate, the presbyterate, and the episcopate.) At the top is the Pope.
Monks, Brother, Nuns, Sisters, Instituted Lectors, Instituted Acolytes, etc are laypersons and are not in the hierarchy of the Church.
When I explain the hierarchy for RCIA I usually write this on the White Board:
Diaconate
Priest
- Diocesan
- Religious Order
- Monsignor
Bishop
- Titular Bishop
- Archbishop (Metropolitan)
- Titular Archbishop
- Cardinal
- Pope
I then give the following explanation.
The Deacon is the lowest order of the clergy and there are two types. Transitional Deacons, who serve at this level for usually a year before they are ordained as Priests, and Permanent Deacons who are ordained to serve as Deacons forever. Permanent Deacons serve a Bishop in a diocese but religious orders will also have Transitional Deacons.
Priests are the next level. Diocesan Priest are the ones you typically see in your Parish and are the Pastors of our individual Parishes. Religious Order Priests belong to a religious order such as the Benedictines and may serve in local Parishes but typically serve their order. Some Priests will be honored with the title Monsignor, but this is not a different rank of the clergy. Monsignor is an ecclesiastical honorific title similar to being made a knight (being called “Sir” or “Chevalier”).
Next is the Bishop. Bishops who given responsibility for the governance of a Diocese, and are also called Suffragan Bishops. A “diocesan bishop” is entrusted with the care of a local Church (diocese). He is responsible for teaching, governing, and sanctifying the faithful of his diocese, sharing these duties with the priests and deacons who serve under him.
There are also Metropolitan Archbishop. The Metropolitan’s powers over dioceses other than his own are normally limited to supervising observance of faith and ecclesiastical discipline and notifying the Supreme Pontiff of any abuses; carrying out, for reasons approved beforehand by the Holy See, a canonical inspection that the Suffragan Bishop has neglected to perform; appointing a diocesan administrator if the college of consultors fails to elect an at least 35-year-old priest within eight days after the vacancy of the see becomes known;[4] and serving as the default ecclesiastical court for appeals from decisions of the tribunals of the Suffragan Bishops.
All Latin rite Metropolitans are Archbishops; however, some Archbishops are not Metropolitans, as there are a few instances where an archdiocese has no suffragans or is itself suffragan to another archdiocese.
Titular Archbishops (i.e. ordained bishops who are given an honorary title to a now-defunct archdiocese; e.g. many Vatican officials and papal nuncios and apostolic delegates are titular archbishops) are never metropolitans. Titular Bishops often serve as Auxiliary Bishops to a Diocesan Bishop.
A Cardinal is a member of the clergy appointed by the Pope to serve in the College of Cardinals, the body empowered to elect someone to the papacy. Most Cardinals are already Bishops when appointed, the majority being Archbishops of important Archdioceses or Patriarchates, the rest already serving as Titular Bishops in the Roman Curia. Recent Popes have appointed a few Priests, most of them renowned theologians, to the College of Cardinals and these have been permitted to decline episcopal ordination.
At the top is the Pope, whose official titles are Bishop of Rome, Vicar of Jesus Christ, Successor of the Prince of the Apostles, Supreme Pontiff of the Universal Church, Primate of Italy, Archbishop and Metropolitan of the Roman Province, Sovereign of the State of Vatican City, and Servant of the Servants of God.
Really, it is that simple, but it seems more confusing when you get into the different titles. It’s not as though a Cardinal or an Archbishop has authority over a bishop. Here’s a bit on some of the common titles: