The Lord's Supper, because of its connection with the supper which the Lord took with his disciples on the eve of his Passion and because it anticipates the wedding feast of the Lamb in the heavenly Jerusalem.
The Breaking of Bread, because Jesus used this rite, part of a Jewish meat when as master of the table he blessed and distributed the bread, above all at the Last Supper. It is by this action that his disciples will recognize him after his Resurrection, and it is this expression that the first Christians will use to designate their Eucharistic assemblies; by doing so they signified that all who eat the one broken bread, Christ, enter into communion with him and form but one body in him.
The Eucharistic assembly (synaxis), because the Eucharist is celebrated amid the assembly of the faithful, the visible expression of the Church.
Source: Catechism of the Catholic Church (Vatican.va)