In the liturgical traditions of Western Christianity, the Epistle side is the term used to designate the side of a church on which the Epistle is read during the Mass or Eucharist. It is the right-hand side of the altar as viewed by the congregation from the nave.

What is the meaning of the Gospel side?

: the left side of an altar or chancel as one faces it.

What are the sides of a church called?

The nave is the main part of the church where the congregation (the people who come to worship) sit. The aisles are the sides of the church which may run along the side of the nave. The transept, if there is one, is an area which crosses the nave near the top of the church.