I AM THAT I AM is the name of God that he revealed to Moses on Mount Sinai.
God told Moses, “I AM THAT I AM. Thus shalt thou say unto the children of Israel, I AM hath sent me unto you… This is my name for ever, and this is my memorial unto all generations.” It is an ancient name, and yet we use it every day. Whenever we say the words, "I am," we are really saying "God in me."

The name, "I AM Presence" corresponds to the Father aspect of God. To Hindus it is Brahma. Buddhists call it Dharmakaya, while Christians think of it as God the Father. It is spirit of God individualized for every one. The ascending and descending triangles of the Trinity of God within man meet in the center of the heart where the name of God, "I AM THAT I AM" is inscribed.

Adapted from Keys to the Kingdom and New Dimensions of Being