Friars are different from monks in that they are called to live the evangelical counsels (vows of poverty, chastity and obedience) in service to society, rather than through cloisteredasceticism and devotion. Whereas monks live in a self-sufficient community, friars work among laypeople and are supported by donations or other charitable support. A monk or nun makes their vows and commits to a particular community in a particular place. Friars commit to a community spread across a wider geographical area known as a province, and so they will typically move around, spending time in different houses of the community within his province.
The English term Friar is derived from the Norman French word frere ("brother"), from the Latinfrater ("brother"), which was widely used in the Latin New Testament to refer to members of the Christian community.
In the Roman Catholic Church, there are two classes of orders known as friars, or mendicant orders: the four "great orders" and the so-called "lesser orders".
The Dominicans, founded ca. 1216. They are also known as the "Friar Preachers", or the "Black Friars", from the black mantle ("cappa") worn over their white habit. The Dominicans were founded by St. Dominic and received papal approval from Honorius III in 1216 as the "Ordo Praedicatorum" under the Rule of St. Augustine. They became a mendicant order in 1221.
The Franciscans, founded in 1209. They are also known as the "Friars Minor" or the "Grey Friars". The Franciscans were founded by St. Francis of Assisi and received oral papal approval by Innocent III in 1209 and formal papal confirmation by Honorius III in 1223. Today the Friars Minor is composed of three branches: the OFM (Brown Franciscans), OFMConv (Grey Friars) and the OFMCap (Capuchins).
The Carmelites, founded ca. 1155. They are also known as the "White Friars" because of the white cloak which covers their brown habit. They received papal approval from Honorius III in 1226 and later by Innocent IV in 1247. The Carmelites were founded as a purely contemplative order, but became mendicants in 1245. There are two types of Carmelites, those of the Ancient Observance (O.Carm.) and those of the Discalced Carmelites (O.C.D.), founded by St. Teresa of Avila in the 16th century.
The Augustinians, founded in 1244 (the "Little Union") and enlarged in 1256 (the "Grand Union"). They are also known as the "Hermits of St. Augustine", or the "Austin Friars". Their rule is based on the writings of Augustine of Hippo. The Augustinians were assembled from various groups of hermits as a mendicant order by Pope Innocent IV in 1244 (Little Union). Additional groups were added by Alexander IV in 1256 (Grand Union).