The Old Believers (starovéry) are Eastern Orthodox Christians who maintain the liturgical and ritual practices of the Eastern Orthodox Church as they existed prior to the reforms of Patriarch Nikon of Moscow between 1652 and 1666. Resisting the accommodation of Russian piety to the contemporary forms of Greek Orthodox worship, these Christians were anathematized, together with their ritual, in a Synod of 1666–67, producing a division in Eastern Europe between the Old Believers and those who followed the state church in its condemnation of the Old Rite.
Old Believers use two fingers while making the Sign of the Cross (the pointer finger straight, middle finger slightly bent) while new-style Orthodoxy uses two fingers and the thumb for the sign of cross,(the thumb and two fingers are held together at point, two fingers folded). Old Ritualists generally say the Jesus Prayer with the Sign of the Cross, while New Ritualists use the Sign of the Cross as a Trinitarian symbol. This makes for a significant difference between the two branches of Russian Orthodoxy, and one of the most noticeable.
Old Believers reject any changes and emendations of liturgical texts and rituals introduced by the reforms of Patriarch Nikon. Thus they continue to use the previous Church Slavonic translation of the Greek texts, including the Psalter, striving to preserve intact the “pre-Nikonian” practices of the Russian Church.
Old Believers only recognize performing baptism through three full immersions, in agreement with the Greek practice, but reject the validity of any baptismal rite performed otherwise (for example through pouring or sprinkling, as the Russian Orthodox Church has occasionally accepted since the 18th century). (See Oblivantsy)
Old Believers perform the Liturgy with seven prosphora, instead of five as in new-rite Russian Orthodoxy or a single large prosphoron, as sometimes done by the Greeks and Arabs. Old Believers do not use polyphonic singing as the new-style Russian practice, but only the monodic, unison singing of Znamenny chant. In this respect it represents a tradition that parallels the use of Byzantine chant and neumatic notation.
In Estonia, there are 2,605 Old Believers according to the 2011 Census. They live mostly in villages from Mustvee to Omedu and from Nina to Varnja on the Western coast of Lake Peipus, and on Piirissaar Island.
Source: Wikipedia.