The 17th century was the time of the split of the Russian Orthodox Church into new believers and old believers. The church reforms of Patriarch Nikon and Tsar Alexei Mikhailovich led to indelible consequences in the life of the Russian Church.
The reforms of Partyriarch Nikon of the 1650s and 1661s were aimed at bringing the divine services of the Orthodox Church to uniformity. The patriarch wanted to correct some mistakes in the ancient Russian liturgical books and bring the rite of the divine service into line with the services of the Church of Constantinople.
Some Christians did not accept the reforms of the liturgical texts. So, the supporters of the old order did not want to leave the double singing of Alleluia and the two-fingered sign. The liturgical books contained corrections to the triple Alleluia, decrees on three fingers.
It should be noted that these moments were perceived by the patriarch as opposing his will, therefore, persecution began against those who did not want to accept the reforms. That is why many Old Believers began to consider Patriarch Nikon the Antichrist and completely rejected the clergy of the Church.
The Old Believers themselves are divided into priests and bespopovtsy. Thus, the former retain their clergy, but the priests consider themselves only true followers of the evangelical Christian doctrine and culture. The difference between priests and Orthodox Christians is their own hierarchy. The bespopovtsy have no clergy at all. This is the hallmark of this religious movement. Bespopovtsy consider the clergy of the Orthodox Church inappropriate and defiled.
In addition to differences in the understanding of the clergy, the Old Believers adhere to the following rules. So, in the minds and practice of Old Believers, there were two fingers, two-fold singing of Alleluia, baptism through compulsory full immersion, the use of only an eight-pointed crucifix (the Orthodox can also use a four-pointed one), the spelling of the name of Christ with one letter "and" - Jesus. Church singing can be considered other distinctive features of the Old Believers. Old Believers do not accept partisan polyphonic singing. Old Believers do not read akathists (with the exception of the most ancient akathist of the Mother of God), there is no worship of the Passion of Christ (Passion), holy hagiasma (water) is considered only that water that is consecrated on the eve of the Baptism of the Lord (for the Orthodox, water is also blessed on the holiday itself).
Of the practical differences between the Old Believers and the Orthodox, one can name the prohibition of the first to shave their beards, adherence to a certain style of clothing. So, some Old Believers still wear caftans, and other clothes are considered sinful.
These are just some of the main differences between Orthodox and Old Believers. In various currents of the Old Believers, there are other dogmatic and moral differences.
It is also worth mentioning that at the present time the curses have been lifted from the Old Believers by the Orthodox Church, with the exception of those denominations of unprofessionalism that have gone into serious heresies.