The term sacrament comes from the Latin word sacramentum, which means oath. According to the history of Israel and other ancient societies, in order to enter into any covenant, an oath must be sworn. God relates to man by means of covenants, just as men of old related to one another primarily through covenants. So if any of us - man or woman, adult or child - are to come into right relationship with God, we need to enter into a covenant (the New Covenant) by means of swearing an oath, a sacrament.
In the New Covenant (the one Jesus established between man and God through his once for all redemptive work), people come into relationship with God by means of an oath. This first oath is what we name baptism. This relationship with God through Jesus is then renewed through other oaths such as receiving the Holy Eucharist.
Through his words and deeds, Jesus personally established seven sacraments by which we enter into and renew our covenantal relationship with God the Father.
Follow the links for descriptions of each sacrament and how one may receive each sacrament.