the Church was Divinely established as a visible society, the salvation of souls is its end, and those who separate themselves from it cut themselves off from God (Epistle to the Philadelphians)

the hierarchy of the Church was instituted by Christ (Epistles to the Philadelphians and the Ephesians)

the threefold character of the hierarchy (Epistle to the Magnesians)

the order of the episcopacy superior by Divine authority to that of the priesthood (Epistles to the Magnesians, Smyraenians, and the Trallians)

the importance of unity of the Church (Epistles to the Trallians, Philadelphians, and the Magnesians)

emphasis on the holiness of the Church (Epistles to the Smyraeans, Ephesians, Magnesians, Trallians, and Romans)

the catholicity of the Church (Letter to the Smyraeans)

the infallibility of the Church (Epistles to the Philadelphians and the Ephesians)

the doctrine of the Eucharist — i.e., belief in Transsubstantiation or the Real Presence of Christ in Communion (Epistle to the Smyraeans)

the Incarnation (Epistle to the Ephesians)

the supernatural virtue of virgnity (Epistle to Polycarp)

the religious character of matrimony (Epistle to Polycarp)

the value of united prayer (Epistle to the Ephesians)

the primacy of the Chair of Peter (Epistle to the Romans, introduction)

a dencouncing of the (later Protestant) doctrine of private judgement in matters of religion (Epistle to the Philadelphians)1

There are three levels of Holy Orders, Deacon, Priest, and Bishop.

Bishops are the Apostles of today. Each one leads a diocese. Special types of bishop are archbishop, cardinal, and pope (who leads the whole Church).

Priests are co-workers of the bishops and can lead a parish. A special title for a priest is monsignor. Priests are called presbyters in the Bible.

Deacons assist the bishop and priests in the celebration of the Eucharist, in the distribution of Holy Communion, in assisting at and blessing marriages, in the proclamation of the Gospel and preaching, in presiding over funerals, and in dedicating themselves to the various ministries of charity.

For more information, see the Catechism of the Catholic Church: http://www.usccb.org/catechism/text/pt2sect2chpt3.htm#iii

With love in Christ.

Bishop – in charge of the spiritual health of a certain geographic area (Diocese). Under the Bishop there are parishes.

Pastor – In charge of a parish within a Diocese.

Monsignor – A pastor but has been awarded that honorific title.

Cardinal – A Bishop that has been awarded that honorific title.

There are Deacons, men who are not priests but are allowed by Church law to perform many functions of priest but they cannot say Mass, hear confessions, etc..