To this question another more precise question may be added : What is a monk ?
A monk is one who in the depths of his heart has perceived the call of Christ : " Go, leave your homeland, your family, leave all your belongings and come, follow me ! "
In faith, the monk has replied : " Yes, here I am, Lord. " And so he enters the monastery where he joins other men who before him and like him have undertaken to follow Christ along the way of the monastic life.