It refers to the intercessory role of the Blessed Virgin Mary as a mediator in the salvific redemption by her son Jesus Christ and that he bestows graces through her.
Its use grew during the Middle Ages and reached its height in the writings of saints Louis de Montfort and Alphonsus Liguori in the 18th century.
[6] Reliance on the intercession of Mary grew and reached its height in the writings of saints Louis de Montfort and Alphonsus Liguori in the 18th century.
[13] Among Catholic theologians, it is undisputed that Jesus Christ is the only mediator between God and the human race, especially in the salvific role of redemption as exhibited by the crucifixion on Mount Calvary.
Mary's function as mother of men in no way obscures or diminishes this unique mediation of Christ, but rather shows its power.
But the Blessed Virgin's salutary influence on men ... flows forth from the superabundance of the merits of Christ, rests on his mediation, depends entirely on it, and draws all its power from it [Lumen gentium, 60].
No creature could ever be counted along with the Incarnate Word and Redeemer; but just as the priesthood of Christ is shared in various ways both by his ministers and the faithful, and as the one goodness of God is radiated in different ways among his creatures, so also the unique mediation of the Redeemer does not exclude but rather gives rise to a manifold cooperation which is but a sharing in this one source [Lumen gentium, 62].
But in virtue of the merits of Jesus Christ, and through the charity which unites them to God and us, the Blessed Virgin and the Saints help us by their intercession to obtain the graces we ask.
Pope Benedict XV allowed the dioceses of Belgium to celebrate the feast of Mary Mediatrix of all graces on May 31 each year.
[20] Other Masses authorized for celebration in different places on the same day were those of the Blessed Virgin Mary Queen of All Saints and Mother of Fair Love and Our Lady of the Sacred Heart of Jesus.