In Mormonism, a quorum is an organized group of priesthood holders who share the same office and responsibilities. For example, there are Aaronic Priesthood quorums for young men (deacons, teachers, priests) and Melchizedek Priesthood quorums for adults (elders and high priests).
Each quorum is presided over by a president and counselors, and members are taught to support one another and carry out assigned duties such as preparing the sacrament, home visits, or teaching. At higher levels, the Quorum of the Twelve Apostles and the Quorums of the Seventy form part of the church’s worldwide leadership.