Just as nuns live in a monastery and live a monastic life, so, too, do monks live in their own monasteries (no coed monasteries) and live a monastic life.
Monastic life in the West is based on the style established by Saint Benedict (480–547 AD) in which the emphasis is on ora et labora (Latin for “prayer and work”). Monastic life is structured on dividing the day between hours of prayer and hours of work. Monks live in “cells” and take a vow of stability in addition to the vows of poverty, chastity, and obedience. That simply means that the monk is attached to community and that physical place (the monastery) until death.
Technically, friars belong to the mendicant orders which were founded in the thirteenth century. Mendicant orders were not cloistered communities as above; rather, they worked among the people, but lived in strict community and took solemn vows.
Two examples of such orders are Franciscans and Dominicans. Saint Francis founded his order in response to an apparition of the Lord in which He instructed him to, “Rebuild My Church.” Francis then founded a little band of men that did just that. They brought religion from the monasteries to the people. They traveled from town to town, preaching, teaching, and dispensing the sacraments. Friars would beg for their daily food and pretty much lived hand-to-mouth.
Dominicans were founded by Saint Dominic in the thirteenth century. They were formed to preach against certain false teachings (heresies) being disseminated. Dominicans would conduct spiritual missions, retreats, and seminars, and travel from town to town, teaching. They lived a strict community life with vows. In the present day, Franciscans and Dominicans continue to live together in friaries and priories. However, they also staff important colleges and universities throughout the world. They were among the first religious to come to the New World to open institutions of high learning and also to convert Native Americans to Catholicism.
There are also monasteries in which men live a cloister life. Many have their roots in the first type of Western Monastic life, the Benedictines. In the sixth century, Saint Benedict established his rule for monastic living, prayer, study, and work. Presently, Benedictines live in community but are not considered cloistered. Most have external apostolates, such as running schools. Trappists and Cistercians live a more secluded life. They are considered contemplative.
During the Counter Reformation, many new religious communities of men were established, each responding to a specific need or to a charism of its founder. Saint Ignatius founded the Jesuits. Jesuits were considered to be the most successful missionary community in the world and won many souls back to Catholicism in areas where Protestantism had a stronghold.
Like the Dominicans, they established centers for higher learning and were some of the best educators in the Catholic Church. Saint John Bosco founded the Salesians in the nineteenth century to help educate poor boys.