WHAT IS THE EUCHARIST?
The Holy Eucharist is a sacrament and a sacrifice. In the Holy Eucharist, under the appearances of bread and wine, the Lord Christ is contained, offered, and received.
(a) The whole Christ is really, truly, and substantially present in the Holy Eucharist. We use the words "really, truly, and substantially" to describe Christ's presence in the Holy Eucharist in order to distinguish Our Lord's teaching from that of mere men who falsely teach that the Holy Eucharist is only a sign or figure of Christ, or that He is present only by His power.
(b) All Christians, with but few minor exceptions, held the true doctrine of the Real Presence from the time of Christ until the Protestant Revolution in the sixteenth century.
(c) The word "Eucharist" means "Thanksgiving."