The English word monk most properly refers to men in monastic life, while the term friar more properly refers to mendicants active in the world (like Franciscans, Dominicans and Augustinians), though not all monasteries require strict enclosure.
Monks and friars both belong to religious orders, but their lifestyles differ, with monks typically residing in monasteries and engaging in contemplative activities, while friars are active in the world as mendicants.