Special thanks to Francisco Raymond Schulte, a Benedictine Monk from St. John’s Abbey in Minnesota, for explaining the difference between a monk and a friar:
A “monk” (from the Greek “monos” as in “one”, “alone”, “single”, “apart”) is a member of one of the ancient (monastic life got started in the deserts of Egypt and Palestine in the 3rd century) cloistered, contemplative religious orders, typically rooted in a particular monastery in a particular place. Monks’ lives are centered on seeking God primarily through prayer, contemplation, meditation. The monks support themselves by the labor of their own hands in that particular place by doing whatever works for them there: some farm, some teach, some make and sell cheese, fruitcakes, bread, jellies, arts and crafts, etc. They are traditionally less involved in “outside” ministry (parishes, missions, etc.) though a number of monastic orders (like us Benedictines) have a centuries-long history of serving in parishes, foreign missions, etc. Whenever the local church is in need the monks of that locale try to assist as best they can.
A “friar” (from the Latin “frater” as in “brother”) is a member of one of the “mendicant” (from the Latin “mendicare” = “to beg”) religious orders (Franciscans and Dominicans are the main ones) started around AD 1200s as an adaptation and alternative to the ancient monastic orders (St. Benedict was born in AD 480). By the 1200s, a time in European history when city-states and independent towns were developing with middle class businessmen, trade, etc., a need was felt for religious orders that were NOT too “rooted” in a particular place — so that they could be “foot loose and fancy free” itinerant preachers: free to wander from town to town, country to country, preaching the Gospel. They did not own property (land or houses would “tie them down”) so they lived simply and depended on the free will gifts of food from the faithful to support themselves in their wanderings. So the friars were called “mendicants”, meaning “beggars”. Eventually they did establish common houses or small monasteries but didn’t live the complicated round of daily prayers that the monks did as their very reason for existing.