I am that I am

I am that I am (Hebrew: אהיה אשר אהיה, pronounced Ehyeh asher ehyeh) is one English translation of the response God used in the Bible when Moses asked for his name (Exodus 3:14). It is one of the most famous verses in the Torah. Hayah means "existed" or "was" in Hebrew; "ehyeh" is the first person singular present/future form. Ehyeh asher ehyeh is generally interpreted to mean I am that I am (King James Bible and others), yet, as indicated, is most literally translated as "I-shall-be that I-shall-be."
Catholic Church interpretation
The Catholic Church's interpretation has been summarized in the Catechism of the Catholic Church, a product of twenty centuries of theology and teaching since the establishment of the Church in the year 33 AD, and adapted from the Catechism of the 16th century Council of Trent. The interpretation is found in numbers 203-213.
Some of the salient points are the following:
206 In revealing his mysterious name, YHWH ("I AM HE WHO IS", "I AM WHO AM" or "I AM WHO I AM"), God says who he is and by what name he is to be called. This divine name is mysterious just as God is mystery. It is at once a name revealed and something like the refusal of a name, and hence it better expresses God as what he is - infinitely above everything that we can understand or say: he is the "hidden God", his name is ineffable, and he is the God who makes himself close to men.
207 God, who reveals his name as "I AM", reveals himself as the God who is always there, present to his people in order to save them.