God revealed himself to his people Israel by making his name known to them. A name expresses a person’s essence and identity and the meaning of this person’s life. God has a name; he is not an anonymous force. To disclose one’s name is to make oneself known to others; in a way it is to hand oneself over by becoming accessible, capable of being known more intimately and addressed personally.
God revealed himself progressively and under different names to his people, but the revelation that proved to be the fundamental one for both the Old and the New Covenants was the revelation of the divine name to Moses in the theophany of the burning bush, on the threshold of the Exodus and of the covenant on Sinai.
The living God
God calls Moses from the midst of a bush that bums without being consumed: “I am the God of your father, the God of Abraham, the God of Isaac, and the God of Jacob.” God is the God of the fathers, the One who had called and guided the patriarchs in their wanderings. He is the faithful and compassionate God who remembers them and his promises; he comes to free their descendants from slavery. He is the God who, from beyond space and time, can do this and wills to do it, the God who will put his almighty power to work for this plan.
“I Am who I Am”
Moses said to God, “If I come to the people of Israel and say to them, ‘The God of your fathers has sent me to you’, and they ask me, ‘What is his name?’ what shall I say to them?” God said to Moses, “I AM WHO I AM.” and he said, “Say this to the people of Israel, ‘I AM has sent me to you’. . . this is my name for ever, and thus I am to be remembered throughout all generations.”
From the Catechism of the Catholic Church 203-205