No. 1360 to 1361, page 343; and No. 1406 to 1408, page 355 of the Catechism of the Catholic Church, Libreria Editrice Vaticana: Urbi Et Orbi Communications:
: The Eucharist is a sacrifice of thanksgiving to the Father, a blessing by which the Church expresses her gratitude to God for all his benefits, for al that he has accomplished through creation, redemption, and sanctification. Eucharist means first of all "thanksgiving."
&bsp; The Eucharist is also the sacrifice of praise by which the Church sings the glory of God in the name of all creation. This sacrifice of praise is possible only through Christ; he unites the faithful to his person, to his praise, and to his intercession, so that the sacrifice of praise to the Father is offered through Christ and with him, to be accepted in him.
Jesus said: "I am the living bread that came down from heaven; if any one eats of this bread, he will live for ever;…he who eats my flesh and drinks my blood has eternal life and…abides in me, and I in him" (Jn 6:51,54,56).
The Eucharist is the heart and the summit of the Church’s life, for in it Christ associates his Church and all her members with his sacrifice of praise and thanksgiving offered once for all on the cross to His Father; by this sacrifice he pours out the graces of salvation on His Body which is the Church.
The Eucharistic celebration always includes: the proclamation of the Word of God; thanksgiving to God the Father for all his benefits, above all the gift of His Son; the consecration of bread and wine; and participation in the liturgical banquet by receiving the Lord’s body and blood. These elements constitute one single act of worship.
From the Baltimore Catechism No. 2; Benziger Brothers, Inc and Tan Books and Publishers, Inc. No. 343
Q: What is the Holy Eucharist?
A: A Sacrament and a sacrifice; in it Our Savior Jesus Christ, body and blood, soul and divinity, under the appearances of bread and wine, is contained, offered, and received.