In The Catechism (Teaching) found on pp 551-552 of the prayer book, we find:
THE SACRAMENTS
Christ has ordained two Sacraments, as generally necessary to salvation; that is to say, Baptism, and the Supper of the Lord, which is the Holy Communion.
What do we mean by “sacrament”?
A sacrament is an outward and visible sign of an inward and spiritual grace, given to us by Christ himself.
The outward sign of baptism is immersion in or pouring over of water with the words “I baptize you …".
The inward grace of baptism is the action of the Holy Spirit giving death to sin and a new birth into righteousness. We are made children of God.
The outward sign in Holy Communion is eating the bread and the wine.
The inward grace of Holy Communion is the action of the Holy Spirit through which we are united with the Living Flesh of the Body of Christ, and His Blood of Forgiveness.
In other words, a sacrament is a two-level action — the physical action and the accompanying spiritual action, where people do the physical part and God takes care of the spiritual part.
As well, article 25 (in the back of the Book of Common Prayer) states (paraphrased):
Even though God really is at work in them, sacraments are not to be worshipped in themselves for only God is to be worshipped. They are a means of us asking God to act, through His Holy Spirit, as He has directed us. Confirmation, penance, holy orders, marriage, and anointing of the sick are also broadly considered sacraments, though the early Anglican Church clarified that only baptism and Holy Communion were explicitly commanded by Christ.
Do you have questions about sacraments, or about how God acts in the world? How have you seen God act through your life?
+David