Canons Regular are priests living in community under a rule ("regula" in Latin), usually the Rule of St. Augustine and thus Augustinian Canons, and sharing their property in common.
Distinct from monks, who live a cloistered, contemplative life and sometimes engage in ministry to those from outside the monastery, the purpose of the life of a canon is to engage in public ministry of liturgy and sacraments for those who visit their churches (historically the monastic life was by its nature lay, whereas canonical life was essentially clerical).
Distinct from Clerks Regular (Regular Clerics)—an example of which is the Society of Jesus—they are members of a particular community of a particular place, and are bound to the public praying of the Liturgy of the Hours in choir.
Secular canons, by contrast, belong to a community of priests attached to a church but do not take vows or live in common under a Rule.
Canons Regular are sometimes called Black or White Canons, depending on the color of the religious habit worn by the congregation to which they belong.
Canons live together in community and take the three vows of chastity, poverty, and obedience; though this is a later development, the first communities of Canons took vows of common property and stability. Some congregations of Canons Regular have retained the vow of stability.
Famous Canons Regular include Pope Adrian IV, Thomas à Kempis, and Desiderius Erasmus.