The sacrament of the Holy Eucharist stands at the center of all the sacraments, as the source and summit of our Faith (CCC 1324). 

In the Eucharist, the body, blood, soul, and divinity of Jesus is truly and substantially present under the appearance of bread and wine.  At every Mass and Divine Liturgy, Christ’s sacrifice on the cross and his victory at the resurrection is made present through the words of consecration spoken by the priest, renewing the mystery of redemption for us today and until the end of time.  In a way that is unique among the sacraments, the Eucharist calls for adoration and devotion, since it is the true presence of Jesus.  In church tabernacles throughout the world, Jesus Christ is sacramentally present in the sacred reserved Eucharistic hosts. 

Since Christ instituted the Eucharist to be the divine food of our spiritual life, “the bread of wayfaring pilgrims,” we draw close to the altar in humility, with consciences clean of serious sin (see Matthew 5:24; 1 Corinthians 11:27–34).  Aware of our constant need for God’s grace and forgiveness, we approach this great sacrament with an attitude like that of the Roman centurion:

“Lord, I am not worthy that you should enter under my roof…” ~ see Matthew 8:5–13

And Christ does indeed enter “under our roof,” becoming our living source of nourishment, making us more like him.  

The Eucharist is the source of the Church herself, the Mystical Body of Christ:

“Because there is one bread, we who are many are one body, for we all partake of the one bread.” ~ 1 Corinthians 10:17

An early prayer of the Church proclaims the foundational nature of the Eucharist:

“Even as this broken bread was scattered over the hills, and was gathered together and became one, so let your Church be gathered together from the ends of the earth into your kingdom.”

The Church is born of the Eucharist, which is the center and source of her life—of her liturgy, prayer, sacraments, and teachings—for it is the very sacrament of Christ’s passion, death, and resurrection.

{excerpt  taken from Ascencion Press "Journey thru the Catechism"}