The Eucharist is the bread or wafer given (along with communion wine) in
Christian communion as set forth in
the Last Supper.
According to transubstantiation, these become the body and blood of Christ in all ways but appearance.
According to consubstantiation, these become simultaneously 100% the body and blood of Christ and 100% ordinary bread and wine.
According to symbolic doctrine, these remain bread and wine but commemorate the Last Supper.