This article focuses on the signs that God has given to demonstrate and confirm his covenant love: the Sabbath, circumcision and baptism as signs of admission, and the Passover meal, and the Lord’s Supper. The article also discusses how baptism has replaced circumcision, and the Lord’s Supper has replaced Passover (among the other OT feasts).
"The sacraments are holy, visible signs and seals. They were instituted by God so that by their use he might the more fully declare and seal to us the promise of the gospel." The article explains aspects of this definition from the Heidelberg Catechism (LD 25) to bring forth the meaning of sacraments.