The sacraments are efficacious signs of grace, instituted by Christ and entrusted to the Church, by which divine life is dispensed to us. The visible rites by which the sacraments are celebrated signify and make present the graces proper to each sacrament. They bear fruit in those who receive them with the required dispositions. —CCC 1131
The seven sacraments are agents through which God gives us grace continually, rather than in a singular, self-contained moment. They are ecclesial mediations between humanity and God, meaning that they bear fruit in the lives of the individual and of the whole community and life of the Church herself. Tangibly reaching to our bodies, minds, and souls in form and matter , in the seven sacraments God uses his Created world to sanctify his Created people. Oil, bread, wine—the stuff of the ordinary—are made holy, imbued by God's grace, and we are transformed in turn by receiving them. The simple, made divine.
You can read more about the sacraments here.