The Eucharist (1)
No form of prayer, or worship, or study is more important for a Catholic than the Mass, and perhaps nothing divides Catholics more fully from most other Christians than the understanding of what is taking place in the Eucharistic celebration that is the Mass.
A Catholic believer is given many gifts, but one stands out above all others. In the words of the Catholic Catechism (CCC 1374):
“In the most blessed sacrament of the Eucharist ‘the body and blood, together with the soul and divinity, of our Lord Jesus Christ and, therefore, the whole Christ is truly, really, and substantially contained.’ "
So Catholics believe that Jesus Christ is really present in the communion host, which we refer to as the Eucharist. We refer to the "substantial" presence of Christ, using the term "substantial" to differentiate the true substance from the appearance of bread and wine.
We believe that the creator of all things comes to each one of us in this intimate way and we use the term “transubstantiation” to describe the unique manner in which Christ becomes sacramentally present through the conversion of the bread and wine into His body and blood. We describe the Eucharist as “the source and summit of the Christian life” (CCC 1324).