The small brown scapular is an outward sign of one's love and devotion to the Mother of God, and an acknowledgment of her special role in His plan of salvation. It is a miniatur model of the larger form worn by members of the Carmelite Order as part of their religious habit.
According to tradition, in the 13th century Our Lady appeared to St. Simon Stock, Superior General of the Order, and gave him the brown scapular saying that whoever wore it would be preserved from eternal damnation and on the 1st Saturday after their death, would be taken by her to heaven.
The wearing of the scapular must be understood to mean that one is striving earnestly to live up to all Christian ideals. It does not take the place of the Church's sacraments, but is an outward sign of inward commitment to virtue and Christian piety, under the patronage of Mary.
The Church teaches us to believe that those who hold an intimate and faithful devotion to the Blessed Virgin Mary will be particularly blessed by her. Thus the wearing of her brown scapular signifies a pledge on our part and a promise on hers. Placing us under her protection, it becomes an aid throughout life to help us maintain the virtues of our vocations. As an outward profession of dedication and trust in Mary, it necessarily calls down special grace, for she would share the sentiments of her Son who said: "If anyone openly declares himself for Me in the presence of men, the Son of Man will declare Himself for him in the presence of God's angels." (Lk. 12:8)
It would be fitting to believe further, that the Mother of God will continue to aid after their deaths those who have served her faithfully, and even that this aid will be especially extended on Saturdays, the day dedicated to her.