That is the name which God announced to Moses from the burning bush. God is He whose existence is absolute. Pair this with the description of God from St. John, that “God is love.”
Taken together, these revelations of God’s identity also reveal the identity of man. Man can only truly exist insofar as he loves and participates in the love of God. That is why the two great commandments are to love God and to love our neighbor. For only in so doing can man fully become a “being” before God, who is Being itself.