Elder D. Todd Christofferson of the Quorum of the Twelve Apostles shares some of his thoughts on this subject.
What Is a Priesthood Quorum?09289_000_042
The scriptures establish the quorums of priesthood and their respective duties in the Church of Jesus Christ today.
Resolve now to do all within your power to make of your priesthood quorum one worthy of the name and one faithful to its mission.
When a priesthood quorum or group meets as a class, its members can learn together, be “nourished by the good word of God” (Moroni 6:4), and grow spiritually.
A quorum is a service unit. Melchizedek and Aaronic Priesthood quorums will find their soul in service.
Each of you who has received an ordination in the priesthood belongs to a quorum. If you live in a place where there are not enough brethren to form a quorum, you are a member of a priesthood group that will become a quorum.
Right: illustrations by Jennifer Tolman