Then he took the bread, said the blessing, broke it, and gave it to them, saying, "This is my body, which will be given for you; do this in memory of me." And likewise the cup, after they had eaten, saying, "This cup is the new covenant in my blood, which will be shed for you."
Luke 22:19-20
As Catholics, we believe the Eucharist is the Real Presence of Jesus Christ. In Consecration, through the hands of a priest and the grace of God, bread and wine are really and truly transubstantiated - transformed in substance - into the body and blood of Christ.
Christ initiated the Eucharist at the Last Supper, the night before He was crucified.