The Mass is frequently called a "memorial," but that word can be confusing in the English-speaking world as it is associated with a variety of meanings.
In the United States, Memorial Day is an observance that recalls those who have died in battle. As a result the word "memorial" is frequently associated with visiting a cemetery.
However, in the Catholic Church the word has a much deeper tradition and is not only tied to remembering a person's death.
Anamnesis
The Catechism of the Catholic Church explains the word in detail in its section on the sacrament of the Eucharist:
The Eucharist is the memorial of Christ's Passover, the making present and the sacramental offering of his unique sacrifice, in the liturgy of the Church which is his Body. In all the Eucharistic Prayers we find after the words of institution a prayer called the anamnesis or memorial.
This means that "memorial" goes beyond a simple remembering, but a mystical "making present" Jesus' sacrifice:
In the sense of Sacred Scripture the memorial is not merely the recollection of past events but the proclamation of the mighty works wrought by God for men. In the liturgical celebration of these events, they become in a certain way present and real. This is how Israel understands its liberation from Egypt: every time Passover is celebrated, the Exodus events are made present to the memory of believers so that they may conform their lives to them.
Spiritually speaking, the sacrifice of Jesus on the cross is not a past event, but an event that is re-lived every time the Mass is celebrated.
While we may not be physically present on Mount Calvary at Mass, we are spiritually transported there in a unique way:
In the New Testament, the memorial takes on new meaning. When the Church celebrates the Eucharist, she commemorates Christ's Passover, and it is made present the sacrifice Christ offered once for all on the cross remains ever present. "As often as the sacrifice of the Cross by which 'Christ our Pasch has been sacrificed' is celebrated on the altar, the work of our redemption is carried out."
With all of this in mind, the Mass is a memorial in a way that goes beyond recalling a past event and instead miraculously brings Christ's sacrifice into the present moment.
