Their Catechism said


236. Q. How does the Church by means of Indulgences remit
the temporal punishment due to sin?

A. The Church by means of Indulgences remits the temporal punishment due
to sin by applying to us the merits of Jesus Christ, and the superabundant
satisfactions of the Blessed Virgin Mary and of the saints; which merits and
satisfactions are its spiritual treasury.

what do they mean when they say, merits of Christ and satisfactions of virgin mary