For Catholics, the Holy Eucharist / Catholic Mass is considered the most important and highest form of prayer. In fact, attending Mass is an obligation, under penalty of mortal sin, each Sunday and on certain other Holy Days of Obligation.
The Mass is divided into two sections, the Liturgy of the Word and the Liturgy of the Eucharist. The Liturgy of the Word consists of two readings (one from the Old Testament and one from the New Testament), the Responsorial Psalm, the Gospel reading, the homily (or sermon), and general intercessions (also called petitions).
The center of the Mass is its second part
The Liturgy of the Holy Eucharist. During this time, Catholics share in the body and blood of Jesus in the form of the bread and wine passed out to the congregation.
According to the Bible, this is done in remembrance of Christ (1 Corinthians 11:23-25, cf. Luke 22:18-20 and Matthew 26:26-28). However, according to the Catechism of the Catholic Church, paragraph 1366, "The Eucharist is thus a sacrifice because it re-presents (makes present) the sacrifice of the cross, because it is its memorial and because it applies its fruit."
The Catechism continues in paragraph 1367: The sacrifice of Christ and the sacrifice of the Holy Eucharist are one single sacrifice: "The victim is one and the same: the same now offers through the ministry of priests, who then offered himself on the cross; only the manner of offering is different."
"And since in this divine sacrifice which is celebrated in the Mass, the same Christ who offered himself once in a bloody manner on the altar of the cross is contained and is offered in an unbloody manner. . . this sacrifice is truly propitiatory."