§1373
Sacraments › … › V. The Sacramental Sacrifice Thanksgiving, Memorial, Presence
The presence of Christ by the power of his word and the Holy Spirit
"Christ Jesus, who died, yes, who was raised from the dead, who is at the right hand of God, who indeed intercedes for us," is present in many ways to his Church: in his word, in his Church's prayer, "where two or three are gathered in my name," in the poor, the sick, and the imprisoned, in the sacraments of which he is the author, in the sacrifice of the Mass, and in the person of the minister. But "he is present . . . Most especially in the Eucharistic species."
Source: Catechism of the Catholic Church (Vatican.va)