It is the bread and wine that by the words of consecration have become the Body and Blood of Jesus Christ.

When the bread and wine are consecrated in the Eucharist, they cease to be simply be bread and wine, and become (respectively), the body and blood of Christ. This inner transformation is referred to as "transubstantiation." Transubstantiation means that while the Body and Blood still retain the outward physical properties of bread and wine, at the words of consecration, their very substance is permanently changed so that they become in fact, the Body and Blood of Christ. (CCC 1374-76)