“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.” (Catechism of the Catholic Church, 1131).
In other words, sacraments are visible signs that make present an invisible reality; this invisible reality is the gift of grace. Whenever a sacrament is celebrated the visible part we see brings about the invisible reality that is taking place.
The seven sacraments of the Church are divided into three groups: