Sacraments [are] outward signs of inward grace, instituted by Christ for our sanctification (Catechismus Council. Trident., II, n. 4, ex S. August "De catechizandis rudibus").
"The saving work of his holy and sanctifying humanity is the sacrament of salvation, which is revealed and active in the Church's sacraments. The seven sacraments are the signs and instruments by which the Holy Spirit spreads the grace of Christ, the Head, throughout the Church, which is his Body"
Catechism of the Catholic Church # 774