Rule of St BenedictBenedict of Nursia left the comfort of the life of a student in Rome in about the year 500 A.D. to seek holiness. He attracted companions in this life, and the plan of life he established for these monastics is known as the Rule of St. Benedict (c. 530). His community eventually founded the monastery of Monte Cassino, between Rome and Naples.
The Rule is summed up in the motto of the Benedictine Order: pax, "peace." The monk or nun's life is divided into regular periods of sleep, prayer, sacred reading, rest, and physical labor. In later periods intellectual work and teaching took the place of farming, crafts, or other forms of manual labor for many - if not most - Christian monastics.
The model for the monastic life under Benedict was the family, with the abbot as father and all the monks as brothers. Priesthood was initially an unimportant part of monasticism - monks used the services of their local pastor. Because of this, female monasticism with an abbess as mother worked as well as male monasticism.
Other rules were written by or are attributed to major monastic founders -- the Rule of St. Pachomius and the Rule of St. Basil in Eastern Orthodoxy and the rules of other western orders. Benedict was undoubtedly aware of them, but to what degree the Rule of St Benedict, was based on a direct knowledge of the those organizations is much debated.
The Benedictine Order, like any organization that lasts more than 1500 years, has had high and low points. In any moment of reform dynamic Benedictine leaders turn back to a life as close to that of the Rule as they can manage.