Answer by
Hieromonk Jog (Gumerov):
Polyeleos is the most festive part of the matins. It
name is Greek in nature: polyeleos from polys – many, and eleos – grace.
Consequently, the literal translation of polyeleos is “all-merciful”. It
consists of singing the lines of psalms 134 (“Praise the name of the Lord,
Alleluia”) and 135 (“Give thanks to the Lord, Alleluia”). The singing is
accompanied by the multiple repetition of the words “For His mercy endures
forever”. This gave the name to this part of the matins.
Polyeleos is served only during the Sunday or festive
liturgy. After the reading of the Gospel, the faithful are anointed with
blessed chrism. This act is not a sacrament but still a sacred rite of the
Church, which serves as a symbol of God’s grace towards us.
During this service all the vigil lamps in the church
are lighted up.
Source: http://pravoslavie.ru/7093.html
CONVERSATION