The schism itself is known as staroobryadchestvo (старообрядчество).
In 1652, Patriarch Nikon of the Russian Orthodox Church introduced a number of reforms aimed at centralizing his power and bringing Russian Orthodox ritual and doctrine in line with those of the Orthodox Church in the post-Byzantine world (e.g., in Greece and elsewhere). The Old Believers rejected Nikon's reforms, becoming labelled raskolniki (раско́льники), (i.e., 'schism-makers'). One of the main figures in the movement was Avvakum Petrovich. Even after the deposition of Nikon (1658), who broached too strong a challenge to the Tsar's authority, a series of church councils officially endorsed the liturgical reforms. Followers of the movement were anathematized at the synod in 1666-1667 and several, including Avvakum, were executed. The Old Believers thenceforce faced heavy persecution until the reign of Tsar Peter the Great, when they began to be tolerated as an extra source of tax revenue. An attempt to make the Old Believers obey the Church was the creation in 1801 of the uni-faith (единоверчество) church.
Early Old Belief was characterized by rejecting "the World" where anti-Christ reigned; they preached about the imminent end of the world, asceticism, adhering to the old rituals and the old faith. Given a lack of bishops and priests, the laity were predominant. One group, the Popovtsy, sought to attract ordained priests and were able to set up an episcopate in the 19th century. The Bespopovtsy, on the other hand, renounced priests and all sacraments, except Baptism.
Old Belief became associated with a strict asceticism that could sometimes be taken to extremes. In the 17th century some groups in Karelia that belonged to the sect committed suicide through self-immolation. Other groups that broke off from the Old Believers practiced castration of men and removal of breasts from women in order to enforce sexual abstinence.
The Old Believers had no official toleration until 1905. In 1971 the Church of Russia lifted the anathemas placed on the Old Believers in the 17th century, but most Old Believer communities have not returned to full communion with other Orthodox Christians.
The Old Believers Today
In the modern day, differences between most Old Believer communities and mainstream Orthodox Christians are in details of ritual practice alone. However, centuries of persecution and the nature of their foundation has made them highly culturally conservative and mistrustful of anything they see as insufficiently Russian. Some Old Believers go so far as to consider any pre-Nikonian Orthodox Russian practice or artifact to be exclusively theirs, denying that the Russian Orthodox Church has any claims upon a history before Patriarch Nikon.
Approximately one million Old Believers remain today, some living in extremely isolated communities in areas of Russia to which they fled centuries ago to avoid persecution. Their life there has been compared by some to America's Amish communities.
A few Old Believer parishes in the United States have entered communion with the Russian Orthodox Church Outside Russia, such as the Church of the Nativity in Erie, Pennsylvania. Another was received into the Greek Orthodox Archdiocese of America by Metropolitan Maximos of Pittsburgh.
Many other Old Believer groups exist, some with teachings and practices that have even less in common with those of the Orthodox Church, even straying into heresy.