The following is taken from the blog The Vineyard of the Saker, a Russian Orthodox, answering a question about the nature of the Church.

@James: What is the Church?

To reply to this question adequately one could write a PhD thesis.  I will try to make a much shorter reply and point you to a few texts, fair enough?

Since you are a former Latin Christian let me begin by saying what the Church is not.  It is not an organization nor a formal institution.  You probably remember that in the Symbol of Faith (aka the Credo) it says “In one Holy, Catholic, and Apostolic Church”.  Most people do not seem to be aware that the words at the very beginning “I believe in” also apply to the section “In one Holy, Catholic, and Apostolic Church”.  In other words, not only do Orthodox Christians believe”in one God, the Father Almighty, Maker of Heaven and Earth and of all things visible and invisible (…) “in one Lord Jesus Christ, the Son of God, the only-begotten, begotten of the Father before all ages. Light of light; true God of true God; begotten, not made; of one essence with the Father, by Whom all things were made” (…) in the Holy Spirit, the Lord, the Giver of Life, Who proceeds from the Father” but also “In one Holy, Catholic, and Apostolic Church“.  The Church itself requires and act of faith similar to the confession of the belief in God.  Orthodox Christians literally “believe in the Church” and this is why the Church is most definitely not an organization.

In theological language the Church is called the Theandric Body of Christ.  Theandric derives from Theanthropos or “Godman” the central dogma of all Christianity.  In other words, the Church is literally the Body of Christ no less than the Eucharist.  This is also why the only valid Mysteries (called “Sacraments” in western theology) can only be found inside that Church.  Just like the Body of Christ, the Church cannot break into parts, have sub-groups, contradict itself, etc.   This is why the Symbol of Faith speaks of ONE Church, no more divisible that God Himself.  Again, to accept that requires an act of faith.

The Church is called “Holy” because it is the Body of Christ and that it is filled with the Holy Spirit.  This is why at the First Apostolic Council in Jerusalem (50 AD) those present wrote “For it seemed good to the Holy Ghost, and to us..” (Acts 15: 28).  However, its individual members – laity and clergy – are not necessarily holy at all.  The Church is also a hospital for sinners and not an elite club of perfect holy people.

The Church is called “Catholic” because of the Greek word καθολικός which means “universal”, especially in the following two meanings: a) which includes and is not limited to one region, country, continent or part of the world and b) acts in a way which includes everybody.  The first one is obvious, but the second one is not.  In this sense, “Catholic” means “Counciliar” in reference to a “council of all” or, in Greek, a “Ecumenical” (including the whole world) council.  The Russian term Соборный/соборность is very accurate here as it clearly points to a council (“sobor” in Russian).  So being “Catholic/Counciliar” means that there is no “teaching Church” versus a “taught Church”, no one instance or clerical rank which is the source of “authority” (to use a Latin concept) or unity.  It is the whole Body of the Church, down to the last layperson, which acting as one has the “authority” of the Church.  Not even a council of, say, 99% of all the Orthodox Bishops – nevermind one bishop or one Patriarch – on the planet can claim to speak for the Church if the rest of the “Body” does not agree with it.  There have been plenty of instances in history were the vast majority of bishops which formally appeared to have remained Orthodox had, in fact, lapsed from the Church.  These are the so-called “robber councils” which, at that time, looked legit and had all the external signs of legitimacy, but which the Body of the Church – the people, really – ended up denouncing and condemning later.  Again, there is no external legitimacy, no authority from which legitimacy can be derived, no person or group of people who can deliver some “certificate of authenticity” to this or that local Church or bishop.

[…]

In the world the visible part of the Church is, for cultural and practical reasons, organized along several independent religious organizations: local Churches, independent (“autocephalous”) Patriarchates which can be Russian, Greek, Paraguayan or Japanese.  The pray in their own language, organize themselves in any way they want, have their own customs and traditions.  Just like there were 12 and 70 apostles there can be plenty local and autonomous Churches as long as they maintain the unity of faith and communion.  In fact, if the One Church did not allow that it would not be truly “Catholic” either.  And just like the Apostles did not have some “Big Boss” over them, the Church has no Head other than Christ Himself.  Sure, for administrative and pastoral issues each Church has a senior bishop (put in charge by a council of local bishops) but even that local boss has no more authority in matters of faith, of confession, that any layperson.  There have been plenty instances in the history of the Church when Patriarchs and entire councils strayed from the truth, and they were often reproved and even condemned by simply lay people.  Speaking of which, there are only 4 clerical ranks in the Church: layperson (yes, that is a rank, a layperson can, in case of emergency, baptize in the name of the entire Church), deacon, priest and bishop. All the other fancy categories are only administrative or honorary. So folks with roaring titles like “His Beatitude the Archbishop of X” is no more than a simple bishop. A Protopresbyter is just a priest and an Archdeacon is just a deacon. Clergymen, by the way, are formally addressed with honorary titles “Most Reverend”, “Your Grace”, etc. but that really applies to the clerical rank, not the person carrying that rank. Same for kissing the hand of a priest – its not because he is so worthy, but because of the high rank (charisma) bestowed on him. He himself might be a dumb jerk (many are) or even a lying hypocritical ignoramus with a bad temper. Remember, the Church is a hospital for sinners, not a club of holy men. There is only one thing that really matters: the confession of faith of this clergyman needs to be 100% Orthodox and his personal sins must not be serious enough to ban him from serving and/or himself receiving the Eucharist (so no pedophilia, no sexual immorality, no killing, no apostasy, etc.).

This is entirely in agreement with the Protestant understanding of the Church. The Church is the entire Body of Christ, not merely a bunch of ecclesiastical officials or even a college of them or system of canon laws or organisation. The entire Body of Christ is the seat of faith, not that of bishops or clerics or councils. Everyone within the Body, from the greatest patriach to the humblest laity, has the “authority” of the Church when speaking from the truth. As the Russian Orthodox theologian and Archpriest Georges Florovsky argues:

The opinions of the Fathers are accepted, not as a formal subjection to outward authority, but because of the inner evidence of their catholic truth. The whole body of the Church has the right of verifying, or, to be more exact, the right, and not only the right but the duty, of certifying. It was in this sense that in the well known Encyclical Letter of 1848 the Eastern Patriarchs wrote that “the people itself” (laos), i.e, the Body of the Church, “was the guardian of piety” (hyperaspistês tês thrêskeias) And even before this the Metropolitan Philaret said the same thing in his Catechism. In answer to the question. “Does a true treasury of sacred tradition exist?” he says “All the faithful, united through the sacred tradition of faith, all together and all successively, are built up by God into one Church, which is the true treasury of sacred tradition, or, to quote the words of St. Paul, ‘The Church of the living God, the pillar and ground of the truth.’

–The Catholicity of the Church

Ironically, it is the Papists and certain Eastern apologists who deny the infallibility of the Church in this sense. What they believe in is not Church infallibility but papal or conciliar infallibility. They believe that Christ’s promise of the rock of the Church pertains only to rare moments of exercise of papal decree or conciliar decision. It is the proper Easterns and the Protestants who have a higher view of Church infallibility as that which pertains to the whole Body of Christ, not merely restricted to certain rare conciliar or papal actions. Especially for the Protestant, we believe that every member of the Church who communicates the Scripture’s meaning rightly speak infallibly for the Scriptures cannot fail in its communication of God’s truth (more here).

The author of this blog is a native Russian, which I think proves the rule that if you want to learn about a high church denomination’s proper teachings, don’t ask a convert, always ask a native who isn’t ideologically invested in exaggerating the difference between their Church and Protestantism to justify their conversion.