The epitrachelion (from the Greek, "around the neck") is the stole worn by priests and bishops as the symbol of their priesthood. This liturgical [OrthodoxWiki:CategoryVestments vestment] is worn around the neck with the two adjacent sides sewn or buttoned together, leaving enough space through which to place the head. It is usually made of brocade with seven embroidered or appliquéd crosses, one at the back of the neck and three down each side.
The priest wears the epitrachelion whenever he is serving as a priest. For some services, e.g. Vespers or Orthros, he wears the epitrachelion by itself. When he is fully vested for the Divine Liturgy, he wears the epitrachelion over the sticharion and under the zone and the phelonion.