The friar movement came out of St. Francis of Assisi. He was the wealthy son of a cloth merchant who gave up everything upon recovery from a life threatening illness. Complete poverty was the driving principle. Francis got (grudging) papal approval, and set off organizing groups of men around Europe. He avoided the traditional monastic set-ups.
The distinction of this group was its extreme poverty and its willingness to help the needy. As the group grew, this was relaxed. There was still extreme suspicion toward money, though.
Important later Franciscans: Bernard of Clairveaux; Bonaventure; Jacopone da Todi; John Duns Scotus; William of Ockham; Angela of Foligno; Ramon Lull.