The terms, "presbyterian" and "episcopalian" do not refer strictly to denominations, but rather to different forms of church "polity", or government. There are three "standard" forms of church polity, those being presbyterianism, the episcopate, and congregationalism.
1. Sola Scriptura. Presby's, and all protestants believe in only the bible as the source of beliefs and doctorine, while the RCC (Roman Catholic Church) teaches that the Bible, and the teachings of the church are the guide for believers lifes. 2. Sola Fide.
So, you ask, what is an Orthodox Presbyterian? Many people hear the word “orthodox” and think we mean “Eastern Orthodox.” We certainly do understand the possible confusion, but our denomination doesn’t have any affiliation with eastern orthodoxy.
Eastern Orthodox Church – 270 million A map of Eastern Orthodoxy by population percentage. The most common estimate of the number of Eastern Orthodox Christians worldwide is 225–300 million, forming a single communion, making it the second largest, single Christian denomination behind the Catholic Church.
Church of Central Africa Presbyterian – 1.3 million; Presbyterian Church of Brazil – 1.0 million; Presbyterian Church in Sudan – 1.0 million ... Minor branches – 1 million Church of the East (Nestorianism) – 0.6 million. Assyrian Church of the East – 0.5 million; Ancient Church of the East – 0.1 million; Messianic Judaism – 0.35 million See also. List of Christian denominations ...
Eastern Orthodox Church, 270 million members. Oriental Orthodoxy, 86 million members. Anglican Communion, 80 million members. Assemblies of God, 67 million members. Calvary Chapel, 25 million members. Evangelical Church in Germany, 21.9 million members. Seventh-day Adventist Church, 20 million members.
Traditionally, Protestantism includes all churches outside of the Roman Catholic and Orthodox Church traditions. Protestant churches affirm the principles of the Protestant Reformation set into motion by Martin Luther’s 95 Theses in 1517. Protestants were first called by that name because they “protested” against the papacy and Roman rule within the Church.
Nontrinitarianism is a form of Christianity that rejects the mainstream Christian doctrine of the Trinity—the teaching that God is three distinct hypostases or persons who are coeternal, coequal, and indivisibly united in one being, or essence (from the Greek ousia).
Roman Catholics believe in an infusement of righteousness, that needs to be maintained by the individual by performance of the sacraments and belonging to the Roman Catholic Church. It is a works righteousness religion, whereas Biblical Christianity is salvation by grace, through faith.