How sad it would be if no one celebrated when we were born, or noticed that we were growing into an adult, or rejoiced at our wedding, or cared enough to comment on our dying.
The rites and sacraments of the church are there to help us remember that God celebrates and notices and rejoices and cares. They are there to get us going on our journey with God and to sustain and nourish our faith along the way. And finally the church is there to commit us for time and eternity into the hands of our loving God.
Over the centuries Christians have called many things sacraments. Lutherans name two sacraments—Holy Baptism and Holy Communion.
There are other religious ceremonies or rites which are important to us too, such as marriage and confirmation, but we don't call them sacraments.
Our criteria for naming something as a sacrament, is to ask three questions: Did Jesus tell us to do it? Does God use it to assure us of God's grace for us? Is there something very physical connected with it; an earthly element? When we consider Baptism and Communion, we can answer yes.