The Catechism of the Catholic Church defines the sacraments as “efficacious signs of grace, instituted by Christ and entrusted to the Church, by which divine life is dispensed to us” (CCC 1131).
To understand what “efficacious” means, it helps to look at how we use signs in our daily lives. Think of a Stop Sign:
A Sacrament is different. It is like a Stop Sign that—by its very nature—physically stops the car for you.
The sacraments do not just tell us a change is happening; they cause the change by the power of the Holy Spirit. As St. Leo the Great said, “what was visible in our Savior has passed over into his mysteries.”
The Church celebrates seven sacraments, which are divided into three categories: Initiation, Healing, and Service (see CCC 1210). Each sacrament has a visible Sign (matter and form) and produces a spiritual Effect (grace).