Sedilia

From Dittopedia

The sedilia (the plural of Latin sedile, seat), in ecclesiastical architecture, the term given to the seats (often) on the south side of the chancel near the altar for the use of the officiating priests. These rebated seats are found in the chancel of churches and monasteries and were for the use of the celebrant and their assistants. The seat is often set back into the main wall of the church itself.