Why is the nun important?

Roman Catholic AnswerThe importance of nuns is something that can not normally be seen and has no importance from a worldly point of view. Monasteries of nuns are viewed as "powerhouses" of prayer, and many great things have been attributed to them over the years even though few ever see them or talk with them. They spent their lives in Adoration and Prayer interceding for all of us.

from Modern Catholic Dictionary by John A. Hardon, S.J. Doubleday & Co., Inc. Garden City, NY 1980

Nun. In general, a member of a religious institute of women, living in a community under the vows of poverty, chastity, and obedience (or Obedience, Stability, and Conversion of Manners in a Benedictine house). More accurately, nuns are religious women under solemn vows living a cloistered, contemplative life in a monastery.