Complex sentence: Normally an abbot is the superior of a monastery, and exercises authority over a religious family of monks-his authority extends only as far as the monastery's walls, or only to the monks who have taken their vows in his monastery.
Split into simpler sentences: Normally an abbot is the superior of a monastery, and exercises authority over a religious family of monks. His authority extends only as far as the monastery's walls, or only to the monks who have taken their vows in his monastery.